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ALBERT R. MANN LIBRARY
New York STATE COLLEGES OF AGRICULTURE AND HoME ECONOMICS
AT
CORNELL UNIVERSITY
Cornell University Library
Parasites and parasitosis of the domesti
Cornell University
The original of this book is in the Cornell University Library.
There are no known copyright restrictions in the United States on the use of the text.
http://www.archive.org/details/cu31924000927016
PARASITES AND PARASITOSIS OF THE DOMESTIC: ANIMALS
eine O« 5S THE MACMILLAN COMPANY
NEW YORK - BOSTON - CHICAGO - DALLAS ATLANTA - SAN FRANCISCO
MACMILLAN & CO., LimitED
LONDON + BOMBAY + CALCUTTA MELBOURNE
THE MACMILLAN CO. OF CANADA, Lt. TORONTO :
PARASITES AND PARASITOSIS
OF THE
DOMESTIC ANIMALS
THE ZOOLOGY AND CONTROL OF THE ANIMAL PARASITES AND THE PATHOGENESIS AND TREATMENT OF PARASITIC DISEASES
BY B. M. UNDERHILL, V.M.D.
PROFESSOR OF PARASITOLOGY AND INSTRUCTOR IN ZOOLOGY AND HISTOLOGY, SCHOOL OF VETERINARY MEDICINE, UNIVER- SITY OF PENNSYLVANIA, ZOOLOGIST, DIVISION OF LABORATORIES, PENNSYLVANIA STATE BUREAU OF ANIMAL INDUSTRY
WITH 180 ILLUSTRATIONS
New York THE MACMILLAN COMPANY
1920
All rights reserved
CopyriaHt, 1920 By THE MACMILLAN COMPANY
Set up and printed. Published April, 1920
PREFACE
In the preparation of this work the author has aimed to present clearly, concisely, and in orderly manner such matter pertaining to the subject at hand as seems most essential to the needs of the student and the practitioner. Notwithstanding its elementary character, the present rapid advances in parasitology have necessitated numerous changes and additions to the manuscript during its preparation. New species and unsettling facts and theories as to some which are not new are, in these days of intensive research, frequently being brought to light and re- ported upon. Some of these findings represent or lead to a distinct advance and, though the observations be in certain cases upon obscure and in themselves unimportant species, they may, by analogy, shed valuable light upon life histories and modes of infection of related forms known to be injurious to domestic animals and man. So frequent are these steps forward that it might almost seem better to leave compara- tive parasitology at the present time to the fragmental attention it has mainly received, and possibly it is to this view that the lack of a recent American volume upon the subject may be attributed. Be that as it may, this book is not intended to be comprehensive, and it contains but little discussion, historical or otherwise, of investigations in the field of medical zoélogy,—limitations which may, in measure, contribute to it a longer period of usefulness in its present form than could be hoped for in an exhaustive treatise. With but few exceptions, the parasites con- sidered are those most likely to be met with and as to which most of the facts pertaining to their biology and pathogenicity have been well established.
The treatment of the subject is based upon the advantages of pre- senting it with at least a rudimental attention to the biologic principles involved in parasitism, a knowledge of which is requisite to the proper conception of parasitology and certainly essential to intelligently applied measures of control. The direct and lucid style of the text throughout will, it is hoped, bring these briefly considered fundamentals before the reader in their true bearing upon the whole subject and render the book particularly acceptable to the general practitioner as well as to the student.
Teachers will appreciate that laboratory work should supplement the class-room method of study. Of course the student should in every case see the parasite under consideration in so far as this is possible. Methods of laboratory technique and the selection of type specimens for
vi PREFACE
dissection should, in the author’s opinion, be left to the teacher, who should certainly be the one best qualified to formulate the course adapted to his needs. No general outline, therefore, as to laboratory methods has been attempted.
If, as has been said, originality is not the best recommendation for a work of this kind, the author feels quite sure that its defects cannot to any great extent be attributed to that source. His observations in the field and laboratory have been utilized in the preparation of the book, but contribute nothing to its pages that is advanced or aggressively critical. Excluding the first three chapters, so much of the subject- matter has been drawn from the published results of the labors of others that the numerous sources cannot well be enumerated here. Acknowl- edgments are especially due to bulletins and articles upon various topics of parasitology written by workers in federal and state bureaus of ex- perimental research. Other sources which have been relied upon and freely used are: M. Neveu-Lemaire’s Parasttologie des Animaux Domes- tiques; Herms’ Medical and Veterinary Entomology; Riley and Johann- sen’s Handbook of Medical Entomology; Calkins’ Protozoology; Neumann’s Parasites and Parasitic Diseases of the Domesticated Animals; Braun’s Animal Parasites of Man; The Journal of Parasitology; The American Edition of Hutyra and Marek, and Osborn’s Economic Zoology.
The author wishes to express his sincere appreciation and thanks to: his laboratory coworker, Dr. Fred Boerner, Jr., for his assistance in the collection of specimens and in the examination of pathologic material; also to Dr. William J. Lentz for his reading and valuable criticism of parts of the manuscript, and to Dr. C. P. Fitch for his helpful suggestions as to sources of reference.
Illustrations for a work of this character will be an aid to the text in proportion as they are exact and well chosen. For the study of mor- phologic characteristics photographs of actual specimens are often too obscure in detail, and accurate drawings or line sketches are, as a rule, of greater service. It will be observed that many of the figures in this book are taken from publications issued by the United States Depart- ment of Agriculture. Probably no better drawings of these subjects have been produced, and the privilege granted to use them is esteemed as a helpful favor of much value to the work. In this connection the author
‘would especially express his gratitude to Dr. L. O. Howard, Chief of the Bureau of Entomology, to Dr. John R. Mohler, Chief of the Bureau of Animal Industry, to Dr. Herbert Osborn, to Dr. Howard Crawley, and to Dr. B. H. Ransom. Finally, thanks are due to Dr. W. H. Hoedt of Philadelphia, for his skill and interest in preparing the photomicro- graphs and many of the drawings.
B. M. U.
Philadelphia, Pa.
CONTENTS
PART I
PRELIMINARY CHAPTERS THE EXTERNAL PARASITES
CHAPTER I INTRODUCTION s 6.5cc.5sd.c tdina ip a tuned ante aasahe mde aed Carman a Manes We A a
Origin of parasitism; Influences inhibiting organic multiplication; The struggle for existence; The sheltered mode of life; Its effect; Phases of the symbiotic relationship; Example of mutualism; Examples of commensalism; True parasitism; Adaptive and degenerative modifications of the parasite; Faculties of parasitic and predatory animals compared; Simplicity, primitive and degnerative; The Tunicata; Functions involved in adaptation to para- sitism; The reproductive process in Melophagus ovinus; Development of the reproductive function in parasites; Parasitism of Gastrophilus intestinalis; Alternation of hosts in life cycle of parasites; The complicated cycle of the liver fluke; The tapeworm as an example of extreme parasitism; Deductions as to the systematic position of parasites through comparison with free-living forms.
CHAPTER II
Forms oF PARASITISM AND INFLUENCE UPON THE HosT................0-005- Terms used in parasitology; Symbiosis; Mutualism; Commensalism; Helotism; Parasitism; Phytoparasites; Zodparasites; Optional occasional parasites; Obligate occasional parasites; Determinate transitory parasites; Permanent parasites; Fixed parasites; Erratic parasites; Determinate erratic parasites; Monoxenous parasites; Heteroxenous parasites; Trans- migration; Incidental or stray parasites; Ectoparasites; Entoparasites; Helminthes; Terms used in the designation of parasitic diseases; Preda- cious and parasitic animals; Factors governing injury to the host by para- sites; General etiologic factors.
CHAPTER III
Puutum I. ARTHROPODA..............-.0 0c eee e ee eee Be deus Gotten Co aati ee Characteristics of the Arthropoda; Characteristics of the class Insecta; Insect methods of reproduction; Duration of life of insects.
viii CONTENTS CHAPTER IV
PAGE
MOSQUITOES AND GNATS. 0.02. ete t eben eens 23
Tse Fires
Characteristics of the order Diptera; Dipterous parasitism; Charactis- tics of the family Culicide; Range and prevalence of mosquitoes; Their breeding habits; Their pathologic importance; The transmitter of malaria; Methods of distinguishing between Anopheles and Culex; The transmitter of yellow fever; Characteristics and habits of the species Ades calopus; Effect of mosquitoes upon live stock; Mosquito control; Characteristics of the family Simuliide; The Southern buffalo gnat; Effect of its attack upon live stock; Control; Protection and treatment.
CHAPTER V
Characteristics of the family Tabanide; Horse-flies; Gad-flies; Effect of their attack; Protection; Characteristics of the family Muscide; The house-fly; Habits of the house-fly and its relation to the transmission of disease; Its control; Protective measures; The horn fly; Its habits; Effect of its attack; Its control; The tsetse flies; Characteristics of the genus Glossina; Distribution and habits of tsetse flies; Their relationship to trypanosomiasis; Investigations by Bruce and others; Tsetse fly control; Characteristics of the family Hippoboscide; The ‘sheep tick” or ‘louse fly;” Its effect; Treatment.
CHAPTER VI
THE DipTeRous LARVE.. 0... cece teeta nes
Tue FLEas
Tue Lice
Myasis; The “screw worm fly;” Its habits; Effect of its attack; Pro- tective measures; Treatment; The flesh flies; The blowfly; Its habits; Protective measures; Characteristics of the family (stride; The horse bot flies; Gaslrophilus intestinalis; Its habits and life history; Effect of the fly and larve upon horses; The red-tailed bot-fly; Its habits and effect; The chin fly; The ox bot or warble flies; Their life history; Their economic im- portance; The sheep bot fly; Its habits and life history; Effect of the at- tack of the fly and its larve; Protection and treatment.
CHAPTER VII
Characteristics of the order Siphonaptera; The dog, cat, and human fleas; Differentiation of species; Life history; Relation of fleas to the transmis- sion of infectious diseases; Treatment and control.
CHAPTER VIII
The sucking lice; Characteristics of the order Siphunculata; The biting lice; Characteristics of the order Mallophaga; Pediculosis of domestic ani-
35
50
65
70
CONTENTS ix
PAGE mals in general; Pediculosis of the horse; Pediculosis of cattle; Pediculosis of the sheep and goat; Pediculosis of the hog; Pediculosis of the dog and cat; Pediculosis of man; Control and treatment of pediculosis.
CHAPTER IX
Licr or Pouttry; THE BEDBUG... 1.0.2.2... tees 82 Prevalence and effect of poultry lice; Species infesting chickens; Species infesting turkeys; Species infesting ducks and geese; Species infesting swan; Species infesting pigeons; Control and treatment of poultry lice; Characteristics of the order Hemiptera; Characteristics of the family Cimi- cidx; The common bedbug; Its habits and effect of its bite; The bedbug as a pest of poultry; Control.
CHAPTER X
Weis MATS. 235s 4 oo Rivne GUA Sn MRR A eis ante CAS DCEO eso me D 94
Characteristics of the class Arachnida; Characteristics of the order Acar-" ina; Parasitism of the Acarina; Acariasis; Characteristics of the family Ga- maside; The gamasid mites of poultry; Habits and effect of their attack; Control; Characteristics of the family Trombidiide; The harvest mites, chiggers, or red bugs; Habits and effect of their attack; Treatment; The mange, scab, or itch mites; Characteristics of the family Sarcoptide; The genera Sarcoptes; Notoedres, Otodectes, Cnemidocoptes, Laminosioptes, Cytoleichus, Psoroptes, and Chorioptes; Their respective characteristics, hosts, and modes of attack; Characteristics of the family Demodecide; Mange and scabies of the various domestic animals; Sarcoptic mange; De- modectic or follicular mange; Notoedric or head mange of the cat and rab- bit; Otodectic or auricular mange; Psoroptic scabies; Auricular scabies of the rabbit; Chorioptic or leg scabies; Symptoms, development, lesions, diag- nosis, and transmission of mange and scabies. ,
CHAPTER XI
TREATMENT OF MANGE AND SCAMIES..........0.0..00 0000 ects 120 General considerations; Treatment of sarcoptic mange ot the horse; Of the dog; Of the goat; Of the sheep; Of cattle; Treatment of notoedric mange of the cat and rabbit; Treatment of demodectic mange; Treatment of oto- dectic mange; Treatment of psoroptic scabies of the sheep; of cattle; Of the horse; Of the rabbit, Treatment of chorioptic scabies of the horse; Of cattle.
CHAPTER XII
MANGE OR POULTRY ie sue teers GP eine ee Geena ea haga ee eee Red ae ee 132 The burrowing mite of poultry; Leg mange or “scaly leg”; Its course and treatment; The depluming mite; The deep-seated acariases of birds; The family Cytoleichidz; The connective tissue mite; The air passage mite.
x CONTENTS CHAPTER XIII
PRE LICKS x45.0-2h aadeutsy ce Gue ai edge dah a Shakes AA Sa dey eee sis sol aCe 136
Structure of ticks in general; Characteristics of the superfamily Ixo- doidea; Characteristics of the family Argaside; The fowl tick; Its habits and effect upon the host; Control; The spinose ear tick; Its habits and effect upon the host; Treatment; Characteristics of the family Ixodide; Description of genera; Species found upon domestic animals in the United States; The Texas-fever or Southern cattle tick; Biological data established by the Zodl- ogical Division of the United States Bureau of Animal Industry; Life his- tory of the Texas-fever tick; Its nonparasitic development; Its parasitic development; Loss occasioned by the Texas-fever tick; Progress made in its eradication; The order Linguatulida; Linguatula rhinaria of the nasal cavi- ties of mammals.
PART II THE INTERNAL PARASITES
CHAPTER XIV
Puytvum IJ. PuatyHetmintues; THE FLuUKES AND TAPEWORMS............ 155
Classification of the parasitic worms; Characteristics of the Platyhelm-
inthes; Characteristics of the class Trematoda; The liver flukes; Their life
history; Prevalence of fascioliasis; Infection; Migration of flukes within the
definitive host and pathogenesis; Fascioliasis of the sheep; Fascioliasis of
cattle; Control and treatment; The blood fluke; Bilharziosis; Characteristics
of the class Cestoda; Characteristics of the family Teeniide; Life history of
tapeworms; Their parasitism.
CHAPTER XV
HLA NTABTS i e lenculss Fis Ged Hun Aes, Hid eG Seen Maa Rate IA ee o BR Ag Be Mee aed Rel ea 174
General consideration of the effect of tapeworms upon their hosts; Tape-
worms of the horse; Tapeworms of cattle, sheep, and goats; Tapeworms of
the dog; Dog tapeworms in relation to human infection; Tapeworms of
the cat; Tapeworms of the rabbit; Characteristics of the family Diphyllo-
bothriide; Occurrence of species; Treatment of teeniasis of the dog; Pre-
vention; Treatment of teniasis of the cat; Treatment of teeniasis of sheep,
goats, and cattle; Treatment of teniasis of the horse.
CHAPTER XVI
TAPEWORMS OF (CHICKENS). .¢4..gs202csemcnganneegacannaea ae oe bu alse me "189 Characteristics of species; Investigations as to their relative occurrence; Symptoms; Control; Treatment.
CONTENTS xi CHAPTER XVII
Tur Tapeworm LARVAE... 2... eee e cent e tenner nnn 194
Pathologic importance; Forms and their characteristics, Cysticercosis
or measles; Beef measles; Its occurrence; Degeneration and vitality of the
cysts; Pork measles, Its occurrence; Degeneration and vitality of the cysts;
Measles of the sheep; Coenurosis or gid; Its occurrence; Its development;
Its post-mortem appearance; Its symptoms; Control and treatment; Echin-
ococcosis or hydatid disease; Structure of the echinococcus cyst; Its de-
velopment; Post-mortem appearance in echinococcosis; Symptoms; Con-
trol.
CHAPTER XVIII
Payitum III. Ca taetmInrHes; Tae Smoors AnD SEGMENTED Rounpworms... 216 Characteristics of the Coelhelminthes; Characteristics of the class Ne- mathelminthes; Characteristics of the order Nematoda: Parasitism of the nematode worms in general; General Considerations as to treatment.
CHAPTER XIX
Nematopa; Famity I. Ascarma#; THe Lance RounpWworms oF THE INTESTINE 229 Characteristics of the Ascaride; Investigations as to life history; Ascar- iasis; Ascarids of the horse; Occurrence of equine ascariasis; Its etiology, control, and treatment; Characteristics of the family Oxyuride; Oxyuriasis of equines; Ascarids of the dog and cat; Ascarids of the hog and sheep; As- carids of the ox; The family Heterakide and heterakiasis of poultry.
CHAPTER XX
Nematopa; FamityIV. Finrarim#; THe THREAD-LIKE WORMS.............. 244 Characteristics of the Filariide; Parasitism; Filaria of the horse; Their oc- currence; Effect of filariasis upon equines; Filaria of sheep and cattle; Filaria of the dog; Hematic filariasis; Filaria of the hog; Filaria of poultry.
CHAPTER XXI
Nematopa; Famity V. Stroneytp#; Supramity I. MrtastroncyLina Worms of THE RESPIRATORY TRACT... 1.0.0.0... 0. cee eee ee eee es 255 Characteristics of the Strongylidez; Parasitism; Strongylosis; Characteris- tics of the Metastrongyline; Parasitism; Bronchial and pulmonary strongy- losis of the sheep and goat; Its symptoms, course, and prognosis; Bronchial and pulmonary strongylosis of cattle; Its symptoms, course, and prog- nosis; Bronchial and pulmonary strongylosis of the pig; Its occurence and symptoms; Bronchial and pulmonary strongylosis of the horse; Cardio- pulmonary strongylosis of the dog; Pulmonary strongylosis of the cat; Post- mortem appearance in bronchial and pulmonary strongylosis; Develop- ment, etiology, control, and treatment of bronchial and pulmonary strongy- losis.
xii
CONTENTS
CHAPTER XXII
PAGE Nematropa; Suspramity II. TricnostroncyLin®=; WoRMS OF THE STOMACH
AND UNTESTING ¢ vic egy veite camnuie aay Agena Loans Sneek Re eG Characteristics of the Trichostrongyline; Parasitism; Gastro-intestinal strongylosis of the sheep and goat; Its occurrence; Its symptoms; Gastro- intestinal strongylosis of cattle; Its occurrence; Its symptoms; Post-mortem appearance in gastro-intestinal strongylosis, Development, etiology, con- trol, and treatment of gastro-intestinal strongylosis.
CHAPTER XXIII
Nematopa; SUBFAMILY III. Srroneyitina; Worms OF THE LARGE AND SMALL
INTESTINES; OTHER STRONGYLES.. 2.0.0.0... eee e eee tenes Characteristics of the Strongyline; Parasitism; Nodular strongylosis of the sheep and goat; Its occurrence;-Its development; Its post-mortem ap- pearance; Its symptoms; Treatment; Nodular strongylosis of cattle; Nodu- lar strongylosis of the hog; Strongylosis of the large intestine of the sheep and goat; Strongylosis of the intestines of the horse; Its development; Its symp- toms; Its post-mortem appearance; Intestinal strongylosis of the dog and eat; Other Strongyline; Tracheal strongylosis of chickens; The kidney worm of the hog; Family Eustrongylide and eustrongylosis.
CHAPTER XXIV
Nematopa; Famity VII. TRICHINELLIDD.........00... 000. ce ees
Characteristics of the Trichinellide; The ‘whip-worms’’ of the large intestine; Trichinella spiralis and trichinosis; Life history of Trichinella spiralis; Intestinal trichinosis; Muscular trichinosis; Degeneration of the trichina cyst; Infection; Symptoms of intestinal and muscular trichinosis in hogs; Trichinosis in rats and mice; Prophylaxis.
CHAPTER XXV
Tur THORN-HEADED WorM; THELEECHES... ........... 0000 cece eee eee
Characteristics of the order Acanthocephala; The thorn-headed worm of the intestines of the hog; Its life history; Its occurrence; Its pathogenicity; Symptoms produced; Treatment; Characteristics of the class Annelida; Characteristics of the order Hirudinea; The horse leech; The medicinal leech; Sources of infestation by leeches; Their effect upon the animal at- tacked; Treatment.
280
306
CONTENTS xiii PART UI THE PATHOGENIC PROTOZOA CHAPTER XXVI PAGE PHYLUM [Vn PROTOZOA oy so fcr oheg ewe G ey ele we Sse Gist sae RES 311
General consideration of the Protozoa; Characters differentiating Pro- tozoa from Metazoa; Ameba, its main features for study; Parasitism of the Protozoa; Progress of research; Relationship of arthropods to infection with protozoal diseases; Evolution of pathogenicity in Protozoa; Methods of reproduction in free and parasitic forms; Life history of the malaria or- ganisms; The schizogonic or asexual cycle; The sporogonic or sexual cycle; Classification of pathogenic species.
CHAPTER XXVII
Tue Protozoan SuspGroups; Diseases DUE TO PROTOZOA... .........-.02055
Characteristics of the class Rhizopoda; Infectious entero-hepatitis of tur- keys; Amebic dysentery of man; Characteristics of the class Flagellata; Characteristics of the order Spirochetida; Spirochetosis of poultry; Char- acteristics of the order Trypanosomatida; Parasitism; Transmission of the infecting organisms; Nagana or “fly disease;”’ Surra, Mal de Caderas; Dourine; Trypanosoma americanum; Characteristics of the class Sporozoa; Characteristics of the order Coccidia; Coccidiosis; Eimeria stiede; Cocci- diosis of rabbits; Diplospora bigemina; Coccidiosis ot dogs; Coccidium zurni; Red dysentery of cattle; Eimeria avium; Coccidial enteritis of chicks; Char- acteristics of the order Hemosporidia; Piroplasma bigeminum; Texas-fever of cattle; Its occurrence; Exposure and development; Its symptoms; The acute type; The chronic type; Prevention and treatment; Characteristics of the order Sarcosporidia; Sarcosporidiosis; Mode of infection.
324
LIST OF ILLUSTRATIONS
FIG. PAGE I, ‘Diagram iof an. sect). a e.2oci6ce see oes dYOR ES aEL ae ade Mee w ER REA 16 2. Diagram of internal parts of an insect. .. ................004. 16 3. Diagram of insect’s heart. 2... 0.02. ee ees 17 4. Mouth parts of a biting insect... ........... 00... cece eee 17 5. Diagram showing tracheal system of an insect.. .............. 18 6. Abdomen of locust, showing spiracles....................-.-.0... 18 7. Head of bee, showing compound eyes, ocelli, and antenne. ... 19 8. Metamorphosis of the house fly....................0.0. 0 0c 19 9. Diagram of segments of arthropod, showing leg muscles, etc...... 19 10. Eggs and larve, of Culex mosquito.... ...........2...000-000. 24 11. Pupa, of Culex and Anopheles mosquitoes ....................5. 26 12. Culex pungens, male and female................... 0.0 c eevee 27 13. Anopheles quadrimaculatus, male and female................... 28 14. Position of Anopheles and Culex at rest.................0.2-... 28 15. Breathing position of larva, of Anopheles and Culex. .......... 29 16. Eggs of Anopheles. ........0.0.00.000 00000 cece ees 30 17. The Southern buffalo gnat. 2.0 2.6... eee eee. 32 18. Larva of Southern buffalo gnat. ..........00.0............... 33 19. Pupa of Southern buffalo gnat..............0.0002.22..0002020.. 33 20: ‘he. black horsedy cuys x2 asediediveas teense eees Serbs are dauees 36 21. The green-head fly. 00. eee 36
22. The stable or stinging fly. 00.2.0... eee 39 23 The horn Fy sec .secocaesa ve dog deals eae dae adieadoen eng edare’ Sede iaahis 42 2A CL SOtSG) HYutule as and goae ed kee eet oe eee ha ewe Sa Roe Neat 44 2: The sheep iG sn) ice Haseena ce aeaan Fame oa Fune hw pau eae Gaby 47 26. The screw word fly aise scant ana aga ohn bow yee woe wien ag qed 51 27. Metamorphosis of the flesh fly................2.....00002 0 eee 52 28. Horse botfly, showing eggs, larva, and adult.................... 54 29. Ox botfly, Hypoderma lineata. .............-.2.2.0.. 0000020 58 30. Ox botfly, Hypoderma bovis........... 00... cece eee ee 59 31. Eggs of Hypoderma lineata... ......... 00. 59 32. Larval stages of Hypoderma lineata.....................0.00... 61 33. The sheep botfly, showing larva, pupa, and adult............... 63 34. The dog flea, anterior portion of body.. ...................... 66 35. The human flea, anterior portion of body ... ..............: -. 66 36. The dog flea, showing development and mouth-parts. .. ...... 67 B04 ava OF MOGs oct auisg wae Shope payee ee Ge ee ee ee a 68 38. Sucking louse of horse, Hematopinus asini. ... .............. 73
XV1
FIG.
39. 40. 41. 42. 43. 44, 45, 46. 47. 48. 49, 50. él. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68.
LIST OF ILLUSTRATIONS
PAGE Biting louse of horse, Trichodectes parumpilosus.. ............. 73 Sucking louse of cattle, Hamatopinus eurysternus. . ” a: Rial, Sucking louse of calves Linognathus (Hematopinus) seit os . 7 Biting louse of cattle, Trichodectes scalaris.. .........-.....-+. 75 Sucking louse of sheep, Linognathus (Heematopinus) pedalis. ... 76 Biting louse of sheep, Trichodectes spherocephalus. ............ 77 Sucking louse of hog, Hematopinus suis..........-...-.---.5555 78 Sucking louse of dog, Linognathus (Hematopinus) piliferus..... 78 Biting louse of dog, Trichodectes latus. ......... 0. ee 79 Louse of the cat, Trichodectes subrostratus..............--..-. 79 Louse of chicken, Goniocotes gigas (G. abdominalis)............ 83 Louse of chicken, Lipeurus caponis (L. variabilis).. .......... 83 Louse of chicken, Menopum trigonocephalum (Menopon pallidum). 83 Louse of turkey, Goniodes stylifer.. ............0..0200e eee 85 Louse of turkey, Lipeurus meleagridis (L. polytrapezius). ..... 85 Louse of turkey, Menopum (Menopon) biseriatum... .......... 85 Louse of duck, Lipeuris anatis (L. squalidus)................... 85 Louse of ducks and geese, Trinotum (Trinoton) luridum. ....... 87 Louse of swan, Philopterus (Docophorus) cygni. ........... meen ST Louse of swan, Ornithonomus (Ornithobius) cygni Daa aan ae aie cian 87 Louse of pigeon, Goniocotes compar................00200 eee eee 87 Louse of pigeon, Goniodes damicornis. .....................000- 87 Bedbug, adult female, mouth-parts ete..........00..........00. 91 Diagram of the anatomy of a spider....................-.0005. 95 Gamasid poultry mite, young and adult...................... 98 Mange mite of horse... «0.0.2... nee 104 Mange mite burrow in human skin. ...................-..05. 105 Colts affected with sarcoptic mange. .................00 000005. 106 Leg scab mite of horse... 6... Le tenes 109
Scab mite of sheep, female............................ pigeesee 111
69. Scab mite of sheep, male... ©... 6. eee 111 70. Follicular mange mite.......0......00000.. 00000 e cece eee 116 71. Mange mite of cat and rabbit...................00..........4. 118 72, Auricular scab mite of rabbit.........00000.0000000 2000 ee 118 73. Portable dipping vat for sheep. 1.0. 1... ee 127 74, Mite of scaly leg of poultry, male and female: jaf 2eteaeses 133 75. Foot of fowl affected with scaly leg... .........00.....00...04. 134 76. Caprbalting. Of tithe 5 a1. 9 chee nae nang tebe Shu Rhee et OGOE ee aR eS 137 77. Capitulum, scutum, and fore leg of Texas fever tick... . ...... 137 78. Stigmal plates of ticks Margaropus, Ixodes, and Dermacentor. .. 138 78a. Photomicrograph of stigmal plate of Texas fever tick........... 138 79. Fowl tick, adult andlarva.............0.0 000000 ccc ce cece cee ee 139 80. Spinose ear tick, nymphal form..................00.00 00 c eee ee 141
FIG. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94, 95. 96. 97. 98. 99.
100.
101.
102.
103.
104.
105.
106.
107.
108.
109.
110.
111.
112.
113.
114,
115.
116.
117.
118.
119.
120.
121.
122.
123,
LIST OF ILLUSTRATIONS
PAGE ‘The castor-bean tick. ............0......0.... baba: emates ese 143 The American dog or wood tick. .... ...... > PERL ese 144 Linguatula rhinaria.. 0... ee ee 153 Planaridnt WOrmn 2s ¢ Gams toes ee ok tee mene Halbnd ates pee e mee 156 Liver fluke, Fasciola hepatica............00.0..0.0...0.0.0 00000000 eee 157 Reproductive organs of liver fluke....................0..222000.. 158 Fasciola hepatica, F. americanus, Dicroccelium lanceatum.. .... 161 Life history of liver fluke... 2.....000000 0.02 eee 162 Blood fluke, male and female.............. FemySapbeweeees eave 168 Segment of Tenia saginata, showing sexual organs. .......... 171 Tapeworms of the horses........ 2.00.2... 000.20 175 Tapeworm of cattle and sheep, Moniezia expansa. =—............. 176 Fringed tapeworm of sheep, anterior segments. = ..... ... 177 Tapeworm of dog, Dipylidium caninum.... ................... 180 Rostellum of Dipylidium caninum.. ........................... 180 Egg packet and Cysticercoid of Dipylidium caninum. ......... 180 Tapeworm of dog, Tenia hydatigena. ......................... 180 Tapeworm of dog, Tenia pisiformis... .............. 00 cee. eee- 180 Tapeworm of dog, Echinococcus granulosus.......... ....... 180 Rostellum of tapeworm of cat, Tenia tenieformis... .. ...... 184 Diphyllobothrium latum.........0000000.00000 000 cee eee 186 Tapeworm of chicken, .Choanotenia infundibuliformis. .......... 189 Scolex of Choanotenia infundibuliformis... .................... 190 Scolex of Davainea tetragona of chicken........................ 190 Scolex of Davainea echinobothrida of chicken................... 190 Tapeworm of man, Tenia saginata............................. 196 Diagram of Cysticercus. . 2. sca. ccrsee neue cul sy yayetsaee nous 198 Fragment of beef muscle, showing cysts of Cysticerus bovis.......... 198 Scoleces of Tenia solium, T. saginata, and Diphyllobothrium latum... 199 Eggs of Tenia saginata and T. solium. ....................... 200 Mature segments of Tenia saginata and T. solium.............. 200 Stages in tapeworm development................. 0.0 e eee eee ee 201 Portions of adult gid tapeworm, Multiceps multiceps............ 205 Diagrammatic section of Multiceps (Ccenurus) cyst. .. ...... 206 Brain of lamb, showing furrows produced by young gid bladderworm.. 206 Gid bladderworm, showing immature tapeworm heads... 206 Diagram of Echinococcus hydatid. .....................0200005. 211 Echinococcus granulosus, showing hydatid with brood capsules....... 214 Transection of Ascaris equi........... 0.00000 eee eee eee eee 217 Posterior extremity of male nematode worm.................... 218 Cephalic extremity of an ascarid worm......................... 229 ORYUTIS! CGM: <5 in4 deter dun Atseh ated weed alae ated Me Atala ei wee erga 236 Belascaris marginata, showing head and maleandfemale. .......... 238
XVill
FIG. 124. 125. 126. 127. 128. 129. 130.
131.
132. 133. 134.
135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150. 151. 152. 153. 154. 155. 156. 157. 158. 159. 160. 161. 162. 163.
LIST OF ILLUSTRATIONS
PAGE Egg of Ascaris lumbricoides. 2.0.00... eee 240 Ascaris lumbricoides, male and female...................--2+255 240 Heterakis perspicillum, male and female, and H. vesicularis of poultry. 242 Setaria labiato-papillosa, male and female........ ......-.....-- 245 Gongylonema scutata, anterior and posterior views. ............ 247 Dirofilaria immitis, male and female... ................ nidies 249
Lung worm of sheep and goat, Dictyocaulus filaria, male, female, and CRIS. cic «ga lbal shh wing anand eau PRA Sea Pee wa ale ave deseee arose 257
Lung worm of sheep, goat, and rabbit, Synthetocaulus rufescens, male and femiale:. giwsiduGiawevdeeaas Le Wee See he Sse aewae gees 257 Lung worm of cattle, Dictyocaulus viviparous... ............. 259 Lung worm of pig, Metastrongylus apri,maleandfemale.. ........ 260
Stomach worm of sheep, goat, and cattle, Hemonchus contortus, female,» o..co. u edad pe eh we RR Se OUD TERS U Re oe eek Paes 269 Hemonchus contortus, anterior portion of body. .............. 269 Hemonchus contortus, enlarged posterior extremity of male. ..... 269 Cooperia curticei, male and female.................2...-...004. 270 Cooperia curticei, enlarged anterior portion ................... 270 Ostertagia marshalli, male and female........................., 270 Trichostrongylus instabilis, male and female... ............... 271 Ostertagia ostertagi, male and female.... ..................... 273 Ostertagia ostertagi, posterior extremity of maleenlarged............ 273 Nematodirus filicollis, male and female and enlarged anterior portion. . 274 Cooperia oncophora, male and female. ....................., 274 (Esophagostomum columbianum, male and female. ............. 282 (CEsophagostomum columbianum, enlarged anterior portion......... 282 Csophagostomum columbianum, enlarged bursa of male.......... 283 (Esophagostomum venulosum, male and female.. ... ......... 283 (Esophagostomum venulosum, enlarged anterior portion... ....... 283 (Esophagostomum venulosum, enlarged bursaofmale.. .. ...... 283 CEsophagostomum radiatum, male and female................... 286 (Esophagostomum radiatum, enlarged anterior portion. .. .... 286 Csophagostomum radiatum, enlarged bursa of male.. ........... 286 Chabertia ovina, male and female.............................. 287 Strongylus equinus, male and female. ..................20005. 288 Hook-worm of dog and cat, Ankylostoma canina, male and female. . 292 Bunostomum phlebotomum, male and female.................... 293 Tracheal worm of poultry, Syngamus trachealis, male and female. . 294 Dioctophyme renale, male...................... ous Sayan s neat 297 Trichuris ovis, male and female.............................005 300 WTriChUris: OVAS. CO. sug oi dak laty pba ons aoa Bie sedeaedce 8 ahs SEW oy Baa 300 Trichinella spiralis, male and female.... ..................... 301
Trichinella spiralis, encysted larva in muscle.................... 302
LIST OF ILLUSTRATIONS xix
FIG. PAGE 164. Trichinella spiralis, microphotograph of cyst.. ...............-. 304 165. The thorn-headed worm, Gigantorhynchus hirudinaceus... .. . 307 166. Cephalic extremity of thorn-headed worm.. .. .............-. 307 Io¢. “Phe horse leechics 4: gu eu Wet ties gam needa & be Mey Neneh aw ee es 308 168. Ameba proteus... 2.0.0... ccc eee 312 169. Spirocheta pallida. 200 occ eee 327 170. Hen suffering from acute spirochetosis.... ..............---4.. 328 171. Piroplasma bigeminum.. ....................... BC Nada tse ble 348 172. Forms of Sarcosporidia, shown in infected muscle.... .......... 351 PuatEs. PaGE I. Texas fever tick, male and female, with details.... ............ 146 II. Texas fever tick, stages of engorgement and details .............. 147 III. Evolution of the parasite of kala-azar.. 2.0.02... eee 317 IV. Life cycle of the malaria parasite. ............00000 0.02220 321 V. Various species of Trypanosoma... ............. cece eee eee 331 VI. Percheron stallion before and after development of dourine... .. 338 VII. Percheron mares, showing chronic dourine and last stage.......... 340 VIII. Coccidian life cycle. ........0 00.0. e cee eee eer 344 TABLES Classification of parasites of the class Insecta.................20e00e. 20 Life history of horse botfly, Gastrophilus equi....................... 55 Life history of sheep botfly, istrus ovis.. 22.0 6... eee eee eee 63 Classification of parasites of the class Arachnida....................... 96 Summary on nonparasitic periods in development of Texas fever tick.... 149 Summary on parasitic periods in development of Texas fever tick... ... 150 Life histories of dog tick and Texas fever tick compared........ ...... 151 Classification of parasites of the phylum Platyhelminthes.............. 157 Life history of liver fluke, Fasciola hepatica......................22.. 163 Life history of beef tapeworm, Tenia saginata.... © ................. 172 The principal tapeworms, with their larve and hosts.... .............. 173 Synopsis of tapeworm larve. .. 0... eee ee 194 Life history of the gid tapeworm, Multiceps multiceps.................., 207 Life history of Echinococcus granulosus.... 2.2.2.0... 000 e ee eeee 213 Classification of parasites of the phylum Gilisla inthe, sedate en: 222 Life history of Trichinella spiralis................... 0000 eee eee eee 303
Classification of parasites of the phylum Protozoa. .................. 322
PARASITES AND PARASITOSIS OF THE DOMESTIC ANIMALS
PARASITES AND PARASITOSIS OF THE DOMESTIC ANIMALS
PART I PRELIMINARY CHAPTERS
THE EXTERNAL PARASITES
CHAPTER I INTRODUCTION
The earth’s vast laboratory of living matter includes a flora and fauna in which all of the highly diversified forms encounter conditions operating to restrict their multiplication and to govern the predominance of cer- tain forms over others. These conditions are constituted, first, by topographic and climatic variations rendering certain localities more or less inhospitable to some organisms, while others may be uninfluenced or perhaps benefited. Second, there is the behavior of living things toward one another; this may be relatively harmonious or there may be an intense rivalry in which organisms encroach or prey one upon the other, the least fit for the strife being driven to less favorable habitats, progres- sively dwarfed, or ultimately becoming extinct. Though most of these inhibitive influences are not apparent to cursory observation, they are, nevertheless, numerous and varied as well as constant in their operation, constituting a prime factor in the evolution and specialization of organic forms.
There is, then, a perpetual struggle for existence, which may lead to the seeking of shelter from the conflict in a changed and often degenerate mode of life to which the organism becomes adaptively modified. Thus, through such influences, a terrestrial animal may be driven to an ar- boreal, or even an aquatic or semiaquatic, existence. A defenseless little member of the Insectivora burrows and becomes subterranean, while another finds protection in the nocturnal habit; others seek the shelter of caves or rock crevices, and we often find creatures, usually somewhat degenerate, in places which seem to us quite unfavorable to their sup- port. While in such cases the animal continues to lead a free and in-
Q PARASITES OF THE DOMESTIC ANIMALS
dependent, often solitary existence, on the other hand, a communion of life’s interests may be established between two organisms which, it is surmised, is founded upon some mutual advantage in the strife. To such association the general term symbiosis has been applied and each of the organisms concerned is referred to as a symbiont. Though there is by no means a uniformity in the application of terms referring to the symbiotic relationship, a usage is adopted here that seems best defined, and by which symbiosis is subdivided into the three categories, (1) mu- tualism, (2) commensalism, and (3) parasitism. In the first there is a reciprocal advantage derived from the union; in the second but one symbiont is benefited though the other suffers no harm, while in the third division one receives an advantage to the detriment of the animal or plant which it invades. There is, however, no sharp line of demarca- tion between these three states of living together, and it may be difficult to determine in some cases whether one or both symbionts receives benefit from the union, or whether one is or is not injured by it.
One of the more obvious examples of mutualism is the case of the hermit crab and the sea anemone. This crab selects a shell, as that of the whelk, for its habitation, from the opening of which it projects only its head and claws. On the surface of the shell may often be found a sea anemone fastened near the opening with its mouth and tentacles in the vicinity of the crab’s head. The anemone in this position not only in a measure serves to conceal the hermit crab from its enemies, but the creature that would prey upon the crab must first reckon with the dangerous stinging threads with which the tentacles of the anemone are armed. The anemone, in its turn, is benefited by being carried about by the crab and aided in this way in obtaining its food.
Such associations are not always of mutual advantage, and may be more in the nature of an invasion of one animal upon or within the body of another, the invading animal alone deriving benefit, while the animal upon which the association is forced, though not benefiting, may in no way suffer from it. A familiar form of this living together (commensalism) is the little crab so commonly found in the shell of the oyster. The oyster is not harmed by its presence, but the crab is bene- fited by the protection which the shell affords. Another more curious example of such association is afforded among the vertebrates by the species of Remora, or suck fishes, which have the first dorsal fin modified into a sucking disk on top of the head. By means of this disk it attaches itself to a shark or other large fish, and is thus carried about, detaching itself only to secure food. Its benefit from such association is in being carried to new feeding grounds without effort of its own, and in the shelter from its enemies which the body of the larger fish may afford. The host, on the other hand, cannot be benefited, nor does it seem to suffer by the presence of its uninvited guest.
INTRODUCTION 3
Whether this relationship between different species is of reciprocal advantage or of benefit to but one, neither of the symbionts lives upon or at the expense of its co-symbiont, and neither has entirely renounced its independence. In true parasitism the invading animal lives upon the tissues of its host, deprives it of a portion of its nourishment; or is in other ways injurious to it. There are many examples of this form of symbiosis, and students of animal life are familiar with the conditions that seem always to attend it, such as the degenerative and adaptive modifications occurring in the parasite.
It is the common habit of many animals, however, to prey upon the bodies of other animals, and we should distinguish, so far as we may, between those which are predatory and those which are parasitic. The former are free and exercise their powers of sense and cunning in snaring or chasing their prey, while the latter, in fully acquired parasitism, live on or in the bodies of their victims, often burrowing into and consuming the body tissues, leading a lazy, beggarly existence in which all of the faculties of special sense and prowess, so highly developed in predatory animals, become degenerate and atrophied.
Parasitism is found throughout the range of animal life from the unicellular to the vertebrate, and, though a sharp distinction between predaceous and parasitic animals may not be made, in view of the de- grading influence of the parasitic habit, the difference between the simplicity of degeneration and the simplicity of primitiveness should be clearly defined. In the development of a primitively simple animal the young stages are more simple than in the adult and it has only simple ancestors. In the degenerate animal, on the other hand, the ancestors are often more complex and the young stages are of a higher grade than the stage of the adult. The adoption of any mode of life which withdraws from the activities necessary to survival in a free existence seems to bring about this condition of degradation. Of this we have a remarkable example outside of the realm of parasitism in the Tunicata. These aberrant animals, in the stage of the free-swimming larva, have a chordal axis which in nearly all of the different species becomes entirely lost before they reach maturity. After passing the “tadpole” stage there follows an extreme specialization to the fixed habit which most tunicates retain throughout their adult life, becoming what are commonly known as sea squirts, mere attached, plant-like sacs, emitting a jet of water when disturbed, and from which all chordate features have been entirely lost.
The degenerative changes which a parasite undergoes concern mostly the nervous system, the organs of locomotion, and those of nutrition, the nervous system becoming reduced to the most indispensable portion, while of the sense-organs nothing may be left except those of touch. The locomotor apparatus may become modified into claws or hooks for
4 PARASITES OF THE DOMESTIC ANIMALS
clasping the hairs of the host, or it may almost if not completely dis- appear and be replaced by such organs of fixation as sucking-disks. As the contents of the alimentary canal or tissue fluids of the host upon which the verminous parasite is nourished need scarcely any digestion, the digestive organs become simplified or may be quite lost, the absorb- tion of nutriment in the latter case taking place entirely through the body integument, as in some of the worms which infest the intestines of man and other animals. The degree of decadence will depend upon the degree of dependence upon the host: In this latter respect the parasitism may be optional, as in the case of the mosquito, which may live upon the juices of plants but prefers a meal of warm blood, or it may be obligate, depending upon another for its means of subsistence, though such obligate parasites as the biting flies, fleas, and bedbugs may also live free and only occasionly visit their hosts, a form of parasitism which may be accompanied by little modification of the adaptability to a free life.
In the event of the parasite becoming progressively degraded into one which not only seeks its host for food, but has become dependent upon it for both its nutrition and place of abode, all of the above mentioned phenomena of adaptation become more conspicuous. There is furnished a very good example of such a transformation in the sheep tick (Melo- phagus ovinus), not a true tick, however, but a fly which, originally an occasional visitor, has, like the louse, taken permanent abode upon its host. No longer taking the aérial flight of its discarded free life, this fly has become wingless, and, furthermore, is enabled to pass its entire life cycle upon the body of the host animal by a remarkable method of reproduction involving the retention of the eggs in the oviducts until development has passed through the larval stage. It is not until ready to pass into the stage of the pupa that the larve are extruded, the pupal case then being attached to the individual wool fibers. From this case the young insect, on becoming sufficiently developed, makes its escape and proceeds to feed and grow, thus rounding out a complete parasitic cycle.
While the easy life of the parasite tends to degeneration, the perpetua- tion of the species becomes more precarious, and the organs of reproduc- tion undergo a marked development. If a host animal dies most of its parasites, especially those existing in the interior of its body, die with it, and, were it not that the eggs find lodgment in a new host, the parasitic species would in a short time become extinct. The transmission of but few of these eggs is successfully accomplished, and in compensation they must be produced in enormous numbers, well protected from the many elements of destruction which they encounter. The mode of reproduc- tion is one of the principal factors determining the conditions of par- asitism, and, while the above modifications pertain more to those
INTRODUCTION 5
dwelling continuously upon or within the bodies of their hosts, we have in the Céstride, among the dipterous insects, a cycle involving internal parasitism during the larval stage, a familiar example being the common horse botfly (Gastrophilus intestinalis), the development of which is © given on page 54. It is plain that a very small percentage of the eggs deposited by this fly can reach the horse’s mouth, and that, having got thus far, many of the larve must be destroyed or pass entirely through the intestinal tract without having succeeded in becoming fixed to the mucous membrane. For this’ there seems to be compensation in the large number of eggs deposited by the persistent female.
While in some cases the complete life cycle of a parasite requires but one host, often, for reasons stated in the foregoing, two successive and generally specifically different hosts are required. A rather compli- cated example of the latter case is the life history of the common liver fluke (Fasciola hepatica), one of the flat worms infesting in its adult state the livers of Herbivora. It will be noted in referring to the cycle of this parasite, given in detail elsewhere (page 160), that it is a very hazardous one, and that its completion must depend upon the co- operation of numerous favorable conditions. The eggs, of which each individual fluke is capable of producing in the neighborhood of one hundred thousand, must reach the exterior amid surroundings favorable to their hatching. If hatched, the larva must escape its many aquatic enemies and within a few hours find a suitable snail host. Providing the snail is not eaten by a duck, or does not otherwise perish during this phase of the cycle, it issues from its host as the free-swimming cercaria, when it is again liable to fall prey to various small aquatic animals. Escaping this and becoming encysted, the chance of any herbivorous animal coming along and swallowing it is very small. The relation of the enormous number of eggs, and the number of individuals which one egg may produce, to the survival of the species amid conditions fraught with such dangers seems quite evident.
In general it may be said as to the propagation of parasites that their prodigious fecundity and the great vital resistance with which most of them are endowed enables species to survive and perpetuate their kind amid varied destroying influences which otherwise would bring about their extermination. The tapeworms inhabiting the intestines of man and other animals, afford another example of extreme parasitism accom- panied by this remarkable development of the reproductive function. Here is a creature so altered to its degenerate existence that it has be- come devoid of mouth and intestine, the body consisting of a scolex, usually referred to as the head, from which are give off segments which remain united until there is formed, as in Tenia saginata of man, a band-shaped colony of from twelve hundred to thirteen hundred or more, passing back from the worm’s attachment to a length which may
6 PARASITES OF THE DOMESTIC ANIMALS
exceed twenty feet. After about the six hundredth, each segment is a mature and sexually complete individual, which later, as it is pushed on by new segments formed at the head, becomes filled with fecundated eggs. By the successive detachment of these ‘‘ripe”’ segments and their passage from the body of the host, it has been estimated that Tenia saginata might throw off in a year as many as one hundred and fifty million eggs, of which but an infinitesimal number, as is quite evident, will reach the body of their proper bovine host for larval development. Again, having been so fortunate, it is improbable that the larve will, while living, reach the intestines of the human host necessary for their further development into adult worms.
Here, then, is an animal well showing the degree of degeneration which may be reached in extreme parasitism; there are no organs of locomotion, no organs of special sense, no organs of digestion, no organs of respiration, and none of true circulation. The body consists of a long band of connected segments, each, when mature, bisexually complete and in itself a sort of independent reproductive individual, the entire energy of the organism concentrated upon the function of reproduction that the perpetuation of the species may be insured amid the perils with which this process is beset.
In many forms permanently parasitic there is an early period of development in which organs of locomotion are distinctly present, but, as the animal matures, these fail to develop or become lost. If it is assumed that this gradual loss of organs, change of structure, and protec- tive transmission of the embryo to an intermediate host is due to the parasitic life, it seems reasonable to conclude that all of the parasitic groups have been derived from free-living forms, and that, as parasitism became a more fixed habit, such structural changes were in the course of time brought about as would make this mode of life obligatory. A re- view of the observed facts, then, in their biologic relationship, leads to the conclusion that symbiosis, of which parasitism is a form, has its causative basis in the struggle for existence, the symbiotic association in more or less measure mitigating the hazards to one or both symbionts. It further follows that, though some forms have undergone an extreme modification, through related contemporary free-living types, their true systematic position may be established.
CHAPTER II FORMS OF PARASITISM AND INFLUENCE UPON THE HOST Forms oF PARASITISM
The student of parasitology will be greatly aided by an orderly and progressive pursuit of the subject, an elementary requisite to which is a broad conception of what is implied by the various terms used in the chapters which are to follow. Those below are not given with the recom- mendation that they be memorized as to the exact wording set forth in their definitions; more essential is such an understanding that examples can readily be picked out, a typical illustration always being in mind for application to the term at hand. With such a conception the student should be able to formulate his own definitions, and this will be of more advantage to him than accepting those set forth according to the con- ceptions of another.
Though some of the following terms have been treated of in foregoing introductory remarks, they are here included for more concise definition and to make the list inclusive.
Symbiosis is the more or less permanent living together of two plants, two animals, or an animal and a plant, the union being in a measure beneficial to both, or to one with or without harm to the other.
Symbiont,—one of two organisms partaking of symbiotic relationship.
Mutualism is a form of symbiosis in which both symbionts are in more or less measure benefited by the union.
Commensalism is that form of symbiosis in which but one symbiont is benefited, while its co-symbiont is neither benefited nor harmed by the union.
Helotism is a form of symbiosis in which one organism appears to enslave the other, enforcing it to labor in its behalf. The term is applied to such association in certain insects.
Parasitism is that form of symbiosis in which one symbiont, for pur- poses of procuring food, or food and shelter, visits briefly, or takes up its abode temporarily or permanently, upon or within the body of its co-symbiont which is harmed by the union. The symbiont receiving the advantage is known as the parasite, to which the one injured is the host.
Phytoparasites are parasites which belong with the vegetable kingdom.
8 PARASITES OF THE DOMESTIC ANIMALS
Zooparasites are parasites which belong with the animal kingdom.
Optional Occasional Parasites are those which only fleetingly visit their hosts to obtain nourishment, but are not dependent upon them for either nourishment or shelter. Example, mosquitoes.
Obligate Occasional Parasites are those which do not permanently live upon their hosts, but are dependent upon them for nourishment and to some extent for shelter. Examples, fleas, bedbugs.
Determinate Transitory Parasites are those in which the parasitism is limited to a definite phase or phases in their life history, during which time the parasitism is obligate and continuous. Examples, botflies, ticks.
Permanent Parasites are those in which the parasitism extends from the hatching of the egg to the stage of reproduction in the adult. Exam- ples, lice, many entozoa.
Fixed Parasites are those which cannot pass spontaneously from one host to another. Examples, larve of botflies, Linguatula, helmin- thes.
Erratic Parasites are those which in their adult state may pass readily from one host to another of the same or different and widely separated species. Examples, mosquitoes, biting flies, ticks, leeches.
Determinate Erratic Parasites are those which may pass from one host to another of the same species, or a species closely allied to the one abandoned. Examples, lice, psoric Acarina.
Monoxenous Parasites are (a) those the eggs of which are expelled by the host, the embryos, while still within the eggs, passing to a new host where hatching and development to the adult occurs. Example, Ascaris.
(b) The eggs having been hatched, the larve are nourished in suitable conditions of moisture and temperature, but cannot undergo further development until they have reached the body of their host. Example, Hemonchus contortus.
Heteroxenous Parasites are (a) those which pass to their definitive host by an intermediate or transitory host, in which they cannot attain their complete development; consequently, a reciprocal transmission between these hosts is essential to the development and propagation of the parasite. Examples, tapeworms, Plasmodium of malaria.
(b) The eggs of the parasite are hatched in the body of the host, the embryos invading the tissues of the same individual host and not at- taining the adult state until they have reached a second host. Example, Trichinella spiralis.
Transmigration is a term applied to the passing of heteroxenous parasites from one host to another.
Incidental or Stray Parasites are those which under natural condi- tions are occasionally found in unusual hosts. Examples, Gigantorhyn-
FORMS OF PARASITISM 9
chus hirudinaceus (specific in pig, incidental in man); Fasciola hepatica (specific in Herbivora, incidental in man).
Ectoparasites (Epizoa) are those which are parasitic to the surface of the body, whether burrowing into the integument, living upon it, or only occasional visitors. Examples, scab mites, ticks, and other Acarina, lice, flies. All of the arthropodal parasites with scarcely an exception.
Endoparasites (Entozoa) are parasites which enter the body of their host, inhabiting its alimentary canal, blood} and other tissues. Exam- ples, Linguatula, larve of the botflies, and almost all of the helminths.
Helminthes is a term under which are grouped all of the worms generally parasitic, with the exception of a small number in which the body is annulated. The group is not a natural zodlogical one and is used mostly in parasitology.
In terms used to designate parasitic diseases it is customary to apply the name of the genus, or other group name to which the parasite be- | longs, as the root, to which is added the suffix asis or osis. As for ex- ample:
Pediculosis, the condition produced by the presence of lice upon the skin; Acariasis, the condition produced by the presence upon the skin of mites and other Acarina; Filariasis, the condition produced by Filaria. And thus we have Ascariasis from Ascaris, Oxyuriasis from Oxyuris, Strongylosis from Strongylide, Trichinosis from Trichinella, Teeniasis from Teeniide, Fascioliasis from Fasciola, Helminthiasis from Helminthes, and Trypanosomiasis from Trypanosoma.
In view of the many factors to be considered, the formulation of exact and limiting interpretations of terms bearing upon kinds of par- asitism is scarcely possible. It cannot be claimed for the above series, therefore, that it is entirely satisfactory as stated and defined. For our conceptions we must rely upon the behavior of the typical rather than the isolated or synthetic, and be content to regard any grouping based upon modes of parasitism as more convenient than exact. It is difficult to circumscribe parasitism; while we speak of the parasitic mode of life as a form of symbiosis, it may well be questioned whether such insects as mosquitoes and biting flies bear a true symbiotic relationship to their hosts; their fleeting visits certainly do not constitute the living together as usually implied by the term. Again, we may not be able to draw a distinct line between certain predaceous and certain parasitic forms. From the more general viewpoint, however, it may be repeated that all predaceous animals voluntarily, by the exercise of their powers of stealth and cunning, seize upon and aim to destroy their prey at once, feeding upon the body. There are parasites which use a degree of stealth in approaching their victims, as certain parasitic Diptera, though the _.invasion of the body of its victim by the parasite is more often passive than voluntary. While the parasite may appropriate a share of the
10 PARASITES OF THE DOMESTIC ANIMALS
nutriment of its host or feed upon its host’s tissues, it is detrimental to the parasite’s welfare to destroy its host. To destroy the body of the animal harboring it would mean the sacrifice of the parasite’s means of subsistence as well as in most cases its shelter. When the host animal dies its internal parasites die with it, and, if it were not for the previously occurring transmission of their offspring to new hosts, the species would rapidly perish. Serious disturbance or death of the host due to its parasites is usually brought about by their presence in large numbers, in which case there is the operation of numerous pathogenic factors. A fatal termination may follow rapidly, but more often there are afebrile morbid phenomena running a prolonged course. In no case is the victim at once destroyed and wholly or in part devoured.
The parasite is always smaller and weaker than its host, and in many cases its influence upon the latter is not observable. It may be said in general that the degree of injury will depend upon the following prin- cipal factors:
InFLUENCE Upon THE Host
1. The Number of Parasites Present.—A tapeworm or one or two ascarids in the intestines may not produce a noticeable effect upon the host. If these parasites are numerous there may be serious disturbances in the host resulting from the deprivation of nutriment which has been appropriated by the infesting worms, from the toxins which they elab- orate, or a more acute effect may be brought about through obstruction of the bowel by large numbers of the parasites in mass.
2. Their Location.—An encysted larva of the beef or pork tapeworm in its usual location will do no observable harm to its host, but if it should lodge in the eye or central nervous system it might give rise to serious disorders. As a rule, intestinal parasites are less harmful than those which invade the blood or respiratory tract, while of the external ‘ parasites, those which burrow into the integument are more injurious than those living upon the surface.
3. The Nature of their Food.—Any parasite which feeds upon the tissues of its host is more harmful than one which merely appropriates a share of the latter’s ingested nutriment. The blood-sucking worms, when present in considerable numbers, bring about serious depletive disturbances, while such worms as the adult ascarids, nourishing mainly upon the residue of food materials, are, in general, less harmful. Sucking lice, armed with piercing mouth parts, are more disturbing to the animal harboring them than the biting lice which feed upon cutaneous débris and the products of their irritation.
4. Their Movements.—Serious pathologic conditions may be brought about by the migrations of parasites or their change from a usual to an unusual position. Muscular trichinosis, the collective
INFLUENCE UPON THE HOST 11
effect of the movement of myriads of embryos of Trichinella spiralis, is a typical instance. An otherwise relatively harmless parasite may work its way into a duct, or, finding lodgment in an unusual organ, set up inflammatory changes and abscess formation. Again, by verminous wandering, fistulous communications may be established between contiguous organs normally possessing no direct connection.
5. Age of Host.—Young animals are predisposed to endoparasitic invasion. To forms which penetrate or are more or less migratory, the more tender tissues of the young offer less resistance than in older animals. Verminous bronchitis is a form of strongylosis observed almost exclusively in animals which are immature. The reduced vitality of old age invites the invasion of both external and internal parasites; there is not only a lessened ability to defend from attack, but reduced activities and secretions of the intestines, skin, and other organs de- crease the capability of eliminating either ecto- or entozoa.
Such external parasites as mosquitoes, flies, ticks, and bedbugs are of greatest pathologic importance as disseminators of infectious diseases, acting either as direct carriers or as intermediate or definitive hosts of the infecting organism. Malaria, Texas fever, and forms of trypan- osomiasis are among diseases which are known to be spread only by this means, while the possibilities as carriers of typhoid and other malignant infections engendered by the habits of the common house fly are well known.
That Helminthes elaborate materials toxic to their host has been demonstrated in experiments with the isolated poisons. It is obvious that, in cases of heavy infestation especially, this toxic effect must be considerably contributed to by the products of decomposition of dead worms.
Etiology.—So varied are the conditions that surround the propaga- tion and existence of parasites that the consideration of the causes of parasitic diseases is best embodied in chapters devoted to their particular occurrence. However, certain circumstances favoring parasitism may be here briefly considered.
Crowded and unclean housing favors the propagation and spread of parasites of both man and domestic animals. For this reason lice and scab mites find their most favorable season in the winter months, when their transmission from animal to animal is facilitated and the reduced activities of the skin offer less resistance to their invasion. Pediculosis and the scab acariases are seldom seen, however, in stables that are well kept, or among animals where due attention is paid to cleanliness of the skin. The summer, on the other hand, is the season of attack by adult parasitic Diptera, and it is during the months at pasture that ticks most rapidly propagate and crawl upon their hosts.
In helminthiasis the influences of environment as an etiologic factor
12 PARASITES OF THE DOMESTIC ANIMALS
are more subordinate to the mode of development of the infecting species. Sheep grazing upon low, marshy land and in the vicinity of ponds are more exposed to infestation with flukes, because there are present conditions essential to the molluscan intermediate host in which the fluke at the stage of the miracidium must find lodgment. Infestation of the pig or the ox with the larve of the tapeworms of man is most likely to occur where untreated human excrement is used as a fertilizer, or where their food may otherwise be directly or indirectly contaminated with such material, while invasion of the human host with the adult worm only occurs after ingestion ofthe tissues of the larval host. The majority of ova of worms expelled by the host fail to find a new host, or meet with unfavorable conditions and are lost. Some, as those of ascarids, are very resistant and may find their proper host after months of exposure to destructive influences. Migration is facilitated to some extent where hatching takes place with the laying of the egg, as in the strongyles of the respiratory tract and in Trichinella. ©
While much remains to be determined as to the life histories of many of the internal parasites, clinical experience indicates that low and wet pasturage, with access to stagnant collections of water, is a strong etiologic factor in helminthiasis, either as harboring possible aquatic intermediate hosts of the worms, or as a vehicle which, directly or by drainage, spreads infestation by dissemination of their germs.
CHAPTER III PHYLUM I. ARTHROPODA
While there are advantages in arranging a description of parasites according to their location, as those of the skin, those of the intestines, those of the liver, those of the circulation, etc., the fact that so many in their life histories pass certain stages in different organs and different species of hosts makes such an arrangement somewhat confused. It seems better, therefore, to treat of the natural history of each parasite in the parasite’s order, essentially including such anatomical and zodlog- ical migrations as may be involved, while at the same time considering its pathogenic influences in these varying locations.
Aside from the phytoparasites, which are not included in this work, the parasites infesting man and domestic animals are distributed among four grand divisions or phyla of the animal kingdom, which, in the order of their zodlogical grade, are Protozoa, Platyhelminthes, Coelhelminthes, and Arthropoda. The last named group contains most all of the external parasites and is the first to be considered in the pages to follow.
As a foundation for the scientific control of parasitism and for the recognition of adaptations to its various forms, at least an elementary knowledge of the structure and habits peculiar to the phylum and its subdivisions to which the parasite belongs is of essential importance. Only the more prominent structural features upon which the separation of the different groups and their subgroups is based will be given here. For more detailed study the student is referred to an advanced text-book in zoology.
The phylum Arthropoda includes such animals as the crayfish, crabs, lobsters, spiders, centipedes, and insects. The body is provided with a hard or leathery external chitinous skeleton divided into a number of segments demarcated externally by constrictions, each segment in the adult, or a certain number of the segments, bearing jointed appendages (Fig. 1). There are usually two or more body regions distinguished by a special modification of the constituant segments. In order that move- ments may take place between the segments of both the body proper and of the appendages, the cuticle at these points is thin and delicate (Fig. 9), forming joints which are protected by an overlapping of the heavier chitinous armor.
All arthropods periodically molt, the process consisting of the break- ing and casting off of the chitinous cuticle after it has loosened from the
14 PARASITES OF THE DOMESTIC ANIMALS
underlying tissue and a new cuticle has been formed. While the cuticle is at first thin and soft, later it becomes hard and unyielding, therefore the moltings are necessary for the accommodation of growth and occur periodically as long as this growth continues. Chitin, to which the firmness of the cuticular exoskeleton is due, is an organic substance in which lime salts may be deposited, as occurs in the Crustacea. The skin is never ciliated, nor do ciliated cells occur in any other organs of the body.
The musculature (Fig. 9) consists of a large number of separate muscles passing from one segment to another and attached at their extremities to the inner side of the skin, their contraction bringing about movements of the segments of the body and appendages one upon the other. They may be attached by so-called tendons, which consist of invaginations of the cuticle surrounded by a corresponding invagination of the epidermis. The muscle fibers are striated and multinuclear.
The digestive tract (Fig. 2) passes directly, or with little flexion, through the body, the mouth being at the anterior end and usually ventral, the anus posterior. Accessory organs, as salivary glands and liver, may or may not be present.
Of the circulatory system (Figs. 2 and 3) the most constant portion is the heart, which is usually tubular and located dorsally. On each side of the organ are openings provided with valves through which the blood passes to be propelled forward. From the large arteries the blood may pass directly into blood sinuses, or it may course through capillaries and veins, though the vascular system is never entirely closed. The blood is usually a colorless fluid with colorless amceboid corpuscles.
In aquatic forms (Crustacea) respiration is by gills, while in the air- breathers it may be by trachee (Figs. 5 and 6), consisting of tubular ramifications from without to within the body, or by peculiar infolding modifications of the integument functioning as lungs. In some of the lower forms respiratory organs are entirely absent, the function in such cases being diffused over the entire body surface.
In various spaces within the bodies of Arthropoda are frequently found fat bodies, a connective tissue the cells of which, richly laden with fat, serve as a store of nourishment. The fact that products of tissue metabolism, such as uric acid, have been found in the fat body, leads to the conclusion that it also acts as a place of storage for substances of excretion before their elimination by the excretory organs, which latter greatly vary in the different groups. In insects and arachnids these organs are represented by the Malpighian tubes, long glandular canals which open into the posterior portion of the digestive tract.
The nervous system consists typically of a ventral chain of ganglia connected by a double longitudinal nerve cord. In well-developed seg- ments the ganglia are large, and a pair of ganglia to each segment might
ARTHROPODA 15
be expected, as in the annelid worms. In the Arthropoda, however, there are differences due to fusion of the segments, in which case there is also fusion of their ganglia. Such fusion is usually accompanied by more or less.shortening of the body, an example of which is afforded by the spiders and crabs where the whole ventral chain unites in a single ganglionic mass. From the most anterior of the ventral ganglia there spring two nerve cords which pass on either side of the esophagus to unite above it with the paired cerebral ganglion or brain, lying in the head. This ganglion remains distinct, its dorsal position preventing its fusion with ganglia of the ventral chain.
Of the sense organs the most highly developed are the eyes, which are compound (Fig. 6), or appear as simple ocelli. In many arthropods there are both of these forms, while others are provided only with ocelli, and in some arthropods eyes are absent. In the compound eyes the cuticle covering them is divided into hexagonal facets, the number of which varies with different groups from a dozen to two thousand or more, each of these areas corresponding to a small chitinous lens. The compound eyes are two in number, while the number of ocelli varies. The latter are very small and have their highest development in the spiders.
With rare exceptions the sexes are separate, and reproduction is generally by fertilized eggs, though parthenogenesis occurs, in some cases having a certain relationship to the life history. Usually the sexes can be readily distinguished by the difference in size and by various modifications of the appendages.
Of the subgroups of the phylum Arthropoda only those containing parasitic species of medical interest will be considered in this work. These are included in the two classes Insecta and Arachnida, which, with scarcely an exception, contain all of the external parasites. It is not correct, however, to say that the arthropodal parasites are exclusively external, as certain insects and arachnids pass a phase of their develop- ment within the bodies of their hosts.
Crass I. INsEcTA
Arthropoda (p. 13).—In number of species the insects constitute the largest of all animal groups. The body is essentially segmented, and is divided into three regions,—head, thorax, and abdomen, which are distinctly marked off from each other (Fig. 1).
The head is usually freely movable at its junction with the thorax, and typically bears on each side a compound eye (Figs. 1 and 7), be- tween which there may be a varying number of simple ocelli.
Arising from the head are a pair of antenne which consist of seg- ments varying in size, shape, and number according to species.
16
PARASITES OF THE DOMESTIC ANIMALS
The mouth parts (Fig. 4) undergo great modification, though all may
be referred to a common type.
Fig. 1.—Diagram of an Insect, with Head and Thoracic Segments Disarticulated: a, head, bearing compound eyes, simple ocelli, and antenne; b, prothorax; c, mesothorax; d, meta- thorax; e, abdomen; f, ovipositor. The pro-, meso-, and metathorax each bear a pair of legs; the meso- and metathorax each a pair of wings. 1, Coxa; 2, trochanter; 3, femur; 4, tibia; 5, tar- sus, terminating in a claw (after Orton, by Dodge; Copyright, 1894, by Harper & Brothers).
This is well presented in its primitive
condition by the grasshopper, in which we have the labrum, or upper lip, represented by a broad unpaired plate situated in front of the mouth. Under the labrum is a pair of strong jaws, the mandibles, each con- sisting of a single unsegmented piece with a cutting inner edge, the two having a lateral move- ment. Following the mandibles is the first pair of maxillee which are prehensile and gustatory in function. These have a num- ber of joints and bear curved and segmented palpi. The sec- ond pair of maxilla are fused to form a single plate,—the la- bium, which is accessory in func- tion to the first pair of max- ille, and, like the latter, bear a pair of segmented palpi. The labium forms the posterior and the labrum the anterior bound- ary of the mouth.
The thorax (Fig. 1) has three
segments, an anterior,—the prothorax, a middle,—the mesothorax,
H i ae a = a = : ——— CR. | ST 7 R / » I = — = os : ke — |. la G Mit 2rq3) : aos a 9 Hed ial ee N MP
Fic. 2.—Diagram of the Principal Internal Anatomical Parts of an Insect: m, mouth; cr, crop; st, stomach; i, lower portion of intestine; a, anus; h, heart; s, salivary glands; c, cerebral ganglion; n, ventral ganglion; Mp, Malpighian tubules; 0, ovaries; g, genital aperature (after
Boas, by Kirkaldy & Pollard).
and a posterior,—the metathorax. somewhat fused.
The last two of these are usually
ARTHROPODA 17
There are three pairs of legs, each thoracic segment bearing one pair (Fig. 1). The leg is divided into five articulated parts,—coxa, trochanter, femur, tibia, and tarsus. The attachment to the body is by the short coxa, to which is joined the trochanter which is also short. Following 74x YS the trochanter are two long segments,—the fe- ges mur and tibia, the former considerably thicker yg, 3.—Diagram of In- than the latter and containing the muscles. The sect’s Heart: c, constriction tarsus, or foot, follows the tibia, and consists of Pe Borg eh a number of short segments, the last bearing aldy & Pollard). hook-like structures, or claws.
Usually there are two pairs of wings arising dorsally from the meso-
Fic. 4.—Mouth-parts of Locust, a biting insect: Labrum, or upper-lip, above, on each side of which are the mandibles, or upper pair of jaws. Labium, or under lip, with labial palpi below. Maxille, or lower pair of jaws, with maxillary palpi, to right and left (from photomicrograph of mounted specimen, by Hoedt).
and metathorax (Fig. 1). They consist, when fully developed, of two closely apposed chitinous outgrowths, between which are extensions of
18 PARASITES OF THE DOMESTIC ANIMALS
the blood sinuses and trachez. Sometimes the anterior, sometimes the posterior pair is the larger, and both may be flexible and adapted for flight. In some insects (beetles) the anterior pair is modified to form wing-shields, or elytra, which are hard, but slightly flexible, structures serving to cover and protect the posterior wings during rest. Some insects possess but one pair of wings (dipterous), while in others wings are entirely absent (apterous).
The abdomen is segmented, the number of segments varying with different groups. Each segment consists of two cuticular plates (Fig. 6), the dorsal tergite and the ventral sternite, which are united laterally by a softer mem- brane, the pleurite. There are no abdominal limbs or limb-like appendages.
Respiration is by trachee (Fig. 5), a system of tubes containing air. These communicate with the outside by the spiracles (Fig. 6), small symmet- rically disposed openings _ located laterally, one pair Fic . 6.—Abdomen of Lo- : on the meso- and cust,s howing Spiracles 1, 2, 3, Fic. 5.—Diagram show- gye pair on the 4,5, 6,7 and 8, one on each side
ing the chief trunks of the of each of the abdominal seg- tracheal system of an in- metathorax and a ments; A, auditory sac (drawn
sect (after Boas, by Kirk- pair on each of the in part from Packard’s Zodl- Ble es Ele, abdominalsegments °2¥)-
except the most posterior. Just inside of the spiracles the trachex are usually united by longitudinal trunks from which are given off fine branches which ramify and anastomose within the body. Respiration is effected by abdominal movements of contraction and expansion.
Insects are mostly oviparous. In some the developed embryo is released from the egg while still within the body of the parent, or this may occur just as the egg is extruded. There are also pupiparous forms where the young pass from the body of the female ready to enter the pupal stage in their development.
In order that the newly hatched larve may be supplied with nourish- ment, the eggs are generally deposited where suitable food is present. In many insects oviposition occurs by means of an ovipositor, a tube- like organ which is developed from the posterior abdominal segments and which may project free from the body or may be retracted into it. In the Hymenoptera the ovipositor may be modified to serve as a sting,
ARTHROPODA
a weapon of defense provided with poison glands. sting is essentially only possessed by the females. Some insects on leaving the egg develop directly to the adult stage,
the larva in most cases differing from the adult prin- cipally in the absence of wings. is a slight change of form with successive molts, the wings being ultimately acquired. Here the meta- morphic process is not thorough, and is therefore referred to as incomplete metamorphosis. jority of insects when hatched from the egg bear no resemblance to the adult, and there is no observ- able gradual approach to this form. characteristically worm-like and an active and vora- cious feeder, a number of molts occurring with the increase in size during this stage. intervenes between the larval and adult stages a period of pupation, during which the animal is quies- cent and aseries of changes
Fic. 9.—Diagram of termi- nal segments of arthropod leg, with muscles. a, articulation;
f, flexors; e, extensors (after Boas, by Kirkaldy & Pollard).
In such cases there
The ma-
The larva is
There then
19
From its nature the
Fic. 7.—Head of
the bee, showing compound eyes, the three ocelli, and the antenne. — Magni- fied (after Orton, by Dodge; Copyright, 1894, by Harper & Brothers).
occur in the body. At the conclusion of these changes the pupal case splits and the imago emerges, which, with
the unfolding of the ap- pendages and hardening of the cuticle, has in all essentials developed into
the complete sexual adult. In this form of development the
changes are distinct, and the process is referred to as complete meta- morphosis (Fig. 8).
The duration of life in insects, including the
‘stages of the egg, larva,
pupa, and adult, usually does not extend beyond a year. With quite a number it is much shorter than this, while with others it may be a matter of several years, an extreme example of larval longevity being
qh 2
@
, Me
t
fey.
Fic. 8. — Metamor- phosis of the House Fly, showing oval, larval, pupal, and adult stages. On the right is an en- largement of the foot; on the left, the foot pad, showing sticky, glandu- lar hairs; on upper left, a tsetse fly (from photo- graph of drawing by author).
20 PARASITES OF THE DOMESTIC ANIMALS
afforded by the seventeen-year cicada. Most of the insect life is occupied by the larval stage, during which the greatest growth takes place. With a few exceptions, as honey bees and ants, the period of the adult is short, in some cases a few days or even hours. The life of the adult is de- voted to the activities concerned in reproduction, and the insect usually dies when this is accomplished.
Of the class Insecta the five following orders contain parasites of medical importance:
Order I. Diptera—Flies, gnats, and mosquitoes.
Order II. Siphonaptera—Fleas.
Order III. Siphunculata—Sucking lice.
Order IV. Mallophaga—Biting lice.
Order V. Hemiptera—Bedbugs and allies.
CLASSIFICATION OF PARASITES OF THE CxiAss INSECTA
Phylum I. Arthropoda. P. 13. Class A. Insecta. P. 15. Order 1. Diptera. P. 28. Family (a) Culicids. Mosquitoes. P. 24. Genus and Species: Culex pungens. Pp. 25, 26. Anopheles quadrimaculatus. P. 26. A. punctipennis. P. 28. Ades calopus. P. 29. Family (b) Simuliide. Buffalo gnats. P. 31. Genus and Species: Simulium pecuarum. Animals attacked, equines and cattle. P. 32. Family (c) Tabanide. Horseflies, gadflies. Animals attacked, equines, cattle. P. 35. Genus and Species: Tabanus atratus. P. 35. T. lineola. P. 36. Family (d) Muscide. House fly and allies. P. 37. Genus and Species: Musca domestica. Injurious to man and domestic animals by irritation and contamination. P. 37. Stomoxys calcitrans. Animals attacked, equines and cattle. P. 39. Lyperosia irritans. Animals attacked, cattle. P. 41. Glossina palpalis. Animals attacked, man, and domestic and wild animals. P. 44. G. morsitans. Animals attacked, same. P. 44. G. longipalpis. Animals attacked, same. P. 44.
ARTHROPODA Q1
Chrysomyia macellaria. Larve attack flesh and mucous surfaces of man and lower animals. P. 50. Sarcophaga sarracenia. Larve attack fresh meat and wounds of animals. P. 52. Calliphora vomitoria. Larve attack fresh and decomposing meat and wounds. P. 52. Family (e) Hippoboscide. P. 47. Genus and Species: Melophagus ovinus. Host, sheep. P. 47. Family (f) Gstride. Botflies. P. 53. Genus and Species: Gastrophilus intestinalis. Host, equines. P. 53. G. hemorrhoidalis. Host, equines. P. 57. G. nasalis. Host, equines. P. 57. Hypoderma lineata. Host, cattle. P. 57. H. bovis. Host, cattle. P. 58. CEstrus ovis. Host, sheep. P. 62. Order 2. Siphonaptera. P. 65. Family (a) Pulicide. Fleas. P. 65. Genus and Species: Ctenocephalus canis. Host, dog. P. 65. C. felis. Host, cat. P. 65. Pulex irritans. Host, man. P. 65. Order 3. Siphunculata. Sucking lice. P. 70. Family (a) Pediculide. P. 70. Genus and Species: Hematopinus asini. Host, equines. P. 73. H. eurysternus. Host, cattle. P. 74. Linognathus vituli. Host, cattle. P. 74. L. pedalis. Host, sheep. P. 76. L. stenopsis. Host, goat. P. 77. Hematopinus suis. Host, hog. P. 77. Linognathus piliferus. Host, dog. P. 78. Pediculus humanus. Host, man. P. 79. P. corporis. Host, man. P. 79. Phthirius pubis. Host, man. P. 79. Order 4. Mallophaga. Biting lice. P. 71. Family (a) Philopteride. P. 71. Genus and Species: Trichodectes equi. Host, equines. P. 73. T. pilosus. Host, equines. P. 73. T. scalaris. Host, cattle. P. 75. T. sphzrocephalus. Host, sheep. P. 76. T. climax. Host, goat. P. 77.
22 PARASITES OF THE DOMESTIC ANIMALS
T. latus. Host, dog. P. 78. T. subrostratus. Host, cat. P. 79. Goniocotes galling. Host, chicken. P. 82. G. gigas. Host, chicken. P. 82. Lipeurus caponis. Host, chicken. P. 83. L. heterographus. Host, chicken. P. 83. Goniodes stylifer. Host, turkey. P. 84. Lipeurus meleagridis. Host, turkey. P. 84. Philopterus icterodes. Hosts, ducks and geese. P. 84. Lipeurus anatis. Hosts, ducks and geese. P. 84. Philopterus cygni. Host, swan. P. 86. Ornithonomus cygni. Host, swan. P. 86. Goniocotes compar. Host, pigeon. P. 86. Goniodes damicornis. Host, pigeon. P. 86. Lipeurus columbz. Host, pigeon. P. 86. Family (b) Liotheide. P. 71. Genus and Species: Menopum trigonocephalum. Host, chicken. P. 83. M. biseriatum. Host, turkey. P. 83. Trinotum luridum. Hosts, ducks and geese. P. 84. T. lituratum. Hosts, ducks and geese. P. 86. Order 5. Hemiptera. P. 89. Family (a) Cimicide. P. 90. Genus and Species: Cimex lectularius. Hosts, man, poultry, ete. P. 90.
CHAPTER IV MOSQUITOES AND GNATS
Order I. Diptera.—Insecta (p. 15). The dipterous insects have only the anterior pair of wings developed, the posterior pair being repre- sented by rudimentary structures called halteres, or balancers, which are supposed to function as organs of balance. In some parasitic forms (sheep ‘‘tick,’”’ bat fly) wings are entirely wanting.
The head, thorax, and abdomen are sharply defined. The mouth parts are adapted for sucking, the haustellum, or sucking tube, being formed by the labium and labrum, within which lie the mandibles and maxille, which may be modified into blade-like structures for piercing. With this structure the insect sucks the juices of plants or penetrates the skin of animals and feeds upon their blood. In the flies the antenne are short, consisting of but three well-developed joints. The three thoracic segments are frequently fused, and the tarsi have five segments.
Metamorphosis is complete. The larve are apodal grubs, maggots, or wrigglers, the latter aquatic (mosquitoes).
Parasitism.—The dipterous group of insects includes a number of species varying in their grade of parasitism from optional occasional to obligate occasional and permanent. They are chiefly of importance from the medical viewpoint as carriers of bacterial and animal parasitic infection, investigations within recent years well establishing the fact that certain serious and often fatal diseases of man and domestic animals are spread by these insects either as essential hosts or as direct carriers of the infecting organism. As essential hosts a part of the development of the pathogenic organism must essentially be undergone in the insect. As direct carriers they may inoculate directly into the blood with con- taminated piercing or biting mouth parts, or they may simply trans- port disease germs upon their bodies and appendages, contaminating wounds, food, or any object upon which they may alight.
As blood-sucking pests and sources of torment in the habitations of man and in the fields and stables of his live stock, many of these two- winged insects are of very considerable economic as well as pathologic importance. In view of all that at the present time can be charged up against them, they are well worthy of the increasing attention they are receiving with a view to their more effectual control.
Of the families of the order Diptera containing parasitic species, six are here considered, as follows:
Q4 PARASITES OF THE DOMESTIC ANIMALS
Family I. Culicidsee—Mosquitoes.
Family II. Simulide—Buffalo gnats. Family III. Tabanidee—Horseflies.
Family IV. Muscidee—House fly and allies. Family V. Hippoboscidaee—Sheep “tick.” Family VI. Gstridse—Botflies.
Famity I. Cunicip®; Mosquitrors
Diptera (p. 23).—The mosquitoes are slender-bodied Diptera with narrow wings which have a distinctive fringe of scale-like hair upon their margins, and in most cases also on each of the wing veins. In the female the proboscis is long, slender, and adapted for piercing. The
Fic. 10.—Egg-mass of Culex pungens, above; young larva, greatly enlarged, at right; young larve, less enlarged, below; enlarged eggs above at left (after Howard, Bul. No. 4, Bureau of Entomology, Dept. of Agr.).
males do not suck blood, differing from the females in the absence of the piercing stylets and in the possession of plumose antenne. Mosquitoes have an adaptation to a very wide range, flourishing equally as well in the frigid regions of the Arctic and Antarctic as in the humid heat of the tropics. Until comparatively recent years few species were known, but more intensive study, in view of their importance as carriers of disease and as pests of man, has brought the mosquito fauna of the world up to about one hundred genera including seven hundred species, of which there are about fifty known in the United States. Breeding Habits.—In the larval stage all the known mosquitoes are aquatic, but such differences occur in their life histories and habits
MOSQUITOES AND GNATS 25
that no one species will serve as typical of the group. In observations conducted by L. O. Howard at Washington, D. C. (1900 Rept.), upon the species Culex pungens it was determined that the eggs were laid upon the water surface in masses of a variety of shapes, often described as boat-shaped because a common form is that of a pointed ellipse (Fig. 10). The number of eggs in each mass varied from two hundred to four hun- dred, all arranged perpendicularly and in longitudinal rows. The in- dividual eggs are slender, somewhat pointed at the tip, and at the bottom broader and blunt, having a length of 0.7 mm. and a diameter of 0.16 mm. at the base.
It has been demonstrated that under the advantageous conditions of the warm summer months eggs may hatch in less than a day from the time they are deposited. The larve, issuing from the under side of the egg mass, are elongate, with head, thorax and abdomen distinct, the head bearing prominent antenne each consisting of a single segment. About the mouth is a mass of prehensile filaments. The abdomen is segmented, and respiration is by trachez which open at the apex by means of the anal siphon. They appear to undergo four molts, and, under favorable conditions, may be transformed into pupz in about seven days. Studied at a period when the larva is nearly full grown, it is seen to remain near the surface of the water with its respiratory tube at the exact surface and its mouth below receiving food which is directed to it by the rotary movements of the mouth filaments. Occa- sionly the larva descends below the surface, but, by a series of wrigglings, quickly returns. The return is only accomplished by considerable exertion, as, once below the surface, the tendency of the larva is to sink rather than to rise. If, therefore, for any reason it is unable to suffi- ciently exert itself to again reach the surface, it will perish. The efficacy of the film of oil spread upon the water may be thus explained; it not only prevents access to the air, but, by its deleterious effect, renders the larva unable to exert sufficient muscular force to recover the position necessary for respiration and buoyancy.
The transformation to the pupal stage, occurring under favorable conditions about the seventh day, is marked by a great enlargement of the thoracic segments (Fig. 11). Here the reverse of the just described physical phenomena obtains; the pupa is lighter than water, and, unlike the larva, effort is required to sink rather than to rise. It remains mo- tionless at the surface, when disturbed descending to the bottom by violent wrigglings. As soon as these exertions cease it will again grad- ually rise. The differential structure of the pupa is noticeable in the enlargement of the thorax, and in that the air tubes no longer open at the abdominal apex, but through two ear-like processes on the thorax, the pupa remaining upright at the water’s surface instead of head down- ward as in the larval stage. Since the adult insect emerges from its
26 PARASITES OF THE DOMESTIC ANIMALS
pupal case at the thorax, there is an apparent adaptability in this re- versal of position.
The common house or “rain barrel’? mosquito of the Northern United States, Culex pungens (Fig. 12), breeds throughout the summer, broods developing wherever there may be standing water, as in pools, troughs, cans, discarded bottles, gutters, ete. The adults of this species may pass the winter in the shelter of darkened retreats, such as the cellars of houses, behind furniture, outbuildings, and wood _ piles, emerging from their hibernation in the spring to deposit their eggs. Many first spring broods in temperate climates hatch from eggs that have been carried over the winter months, the eggs seeming to stand desiccation in cry locations to promptly hatch in pools left by the spring
Fig. 11.—Pupa of Culex pungens at left; pupa of Anopheles quad- rimaculatus at right—greatly enlarged (after Howard, Bul. No. 25, Bureau of Entomology, Dept. of Agr.).
rains, or even in water from melting snow during the warmer days of late winter.
In refutation of the assertion often made that mosquitoes cannot ovulate without a meal of warm blood, it has been demonstrated in experiments upon some of our common blood-sucking species that fe- males as well as males can not only be kept alive for a Jong period when given access only to plants, but will, under such conditions, repeatedly breed.
Pathologic Importance.— While their preference for blood has made them of primary general interest as pests in the habitations of man, mosquitoes are of the greatest importance medically, not only as possible direct transmitters of disease, but as specific bearers of infection, bring- ing about such diseases as malaria, yellow fever, and possibly filariasis. There have been many convincing demonstrations that malaria is transmitted exclusively by the bite of mosquitoes, only, however, by species belonging with the anopheles group, of which Anopheles quadri-
MOSQUITOES AND GNATS
Fic. 12.—Culex pungens: a, female, from side; b, male, from above; c, front tarsus of same; d, middle tarsus; e, hind tarsus; f, genitalia of same, i, scales from hind border of wing; h, scales from disk of wing—enlarged (after Howard, Bul. No. 4, Bureau of Entomology, Dept. of Agr.).
28 PARASITES OF THE DOMESTIC ANIMALS
maculatus (Fig. 13) and A. punctipennis have been most often observed in the United States. While elaborate keys and tables are necessary even to the entomologist for more exact differentiation, it is not a difficult . matter to decide whether a mosquito is or is not a transmitter of malaria,
Fig. 13.—Anopheles quadrimaculatus: Adult: male at left, fe- male at right—enlarged (after Howard, Bul. No. 25, Bureau of Entomology, Dept. of Agr.).
the two genera Culex and Anopheles being readily distinguished by the following more prominent characteristics: The adult Culex, when at rest upon a wall, usually holds the body
TOE “Z
Fia. 14.—Anopheles at left, Culex at right—enlarged (after Howard, Bul. No. 25, Bureau of Entomology, Dept. of Agr.).
parallel with the wall, or with the abdomen slightly inclined toward it, the angle formed by the abdomen with the head and thorax giving a
MOSQUITOES AND GNATS 29
hunchback appearance. The proboscis projects forward but not suffi- ciently so as to be on a line with the axis of the body (Fig. 14). The palpi in the female are short, in the male usually long. The wings, as a rule, are without spots.
Adults of the anopheles group when thus at rest hold the body at an angle of about forty-five degrees with the wall’s surface, the abdomen directed outward (Fig. 14). The proboscis projects forward on a line with the axis of the body. In both sexes the palpi are about as long as the proboscis. The wings are usually spotted.
The larva of Culex, when at the surface of the water, rests in an oblique or vertical position with the re-. spiratory tube at the exact surface (Fig. 15).
The resting larva of Anopheles floats in a horizontal position just beneath the surface. There is no respiratory tube, the spiracles opening on the eighth abdominal segment which is applied to ny the surface (Fig. 15). nies
Eggs of Culex are de- Fig. 15.—At top, half grown larva of Anopheles in posited upon water in breathing position, just beneath the surface film. At masses, the rafts of e ees bottom, half grown larva of Culex in breathing position
2 —greatly enlarged (after Howard, Bul. No. 25, Bureau often being more or less of Entomology, Dept. of Agr.).
boat-shaped (Fig. 10).
Anopheles lay their eggs upon water unmassed, the eggs floating singly by lateral expansions (Fig. 16).
The mosquito breeding in our Southern States which carries yellow fever from man to man, Aides calopus (Stegomya calopus, S. fasciata), is rather peculiarly marked. Upon each side of the thorax is a broad, silvery, curved line, between which there are two parallel median lines and a slender discontinuous line, the whole pattern presenting somewhat
30 PARASITES OF THE DOMESTIC ANIMALS
the shape of alyre. At the base of each abdominal segment is a narrow, silvery band, while on each side there is a silvery spot. At the base of each segment of the black legs there is a distinct white band.
Highly domestic, this species will breed in collections of water about and within the habitations of man, the larve often being found in small household water receptacles, such as flower pots, vases, etc. Of its habits acquired by long association with man, Howard thus speaks: “It approaches stealthily from behind, retreating upon the slightest alarm.
Fic. 16.—Group of eggs of Anopheles quadrimaculatus as they appear resting naturally on the surface of the water—enlarged (after Howard, Bul. No. 25, Bureau of Entomology, Dept. of Agr.).
The ankles and, when one is sitting at a table or desk, the under side of the hands and wrists are favorable points of attack. It attacks silently, whereas other mosquitoes have a piping or humming note. The warning sound has doubtless been suppressed in the evolutionary process of its adaptation to man. It is extremely wary. It hides whenever it can, concealing itself in garments, working into the pockets and under the lapels of coats, and crawling up under the clothes to bite the legs. In houses it will hide in dark corners, under picture moldings and behind the heads of old-fashioned bedsteads. It will enter closets and hide in the folds of garments.”
MOSQUITOES AND GNATS 31
Effect upon Live Stock.—That mosquitoes are a source of much annoyance and actual suffering to live stock can be attested to by stock- men. Horses and cattle pasturing upon low lands and amid vegetation where the insects abound are especially exposed to attack, the pests often hovering about them in clouds, while upon the bodies of the animals large numbers may be seen with abdomens engorged with the blood of their victims. Loss of condition and the falling off of produc- tiveness in dairy herds must essentially follow this interference with their pasturage and comfort.
Control.—The most effectual preventive measures dealing with mos- quitoes are those directed against the larvee. The abolition of breeding places being of first importance, all receptacles for standing water, such as rain barrels, cans, vaults, gutters, etc., should be removed, covered, or otherwise made impossible to access and propagation of mosquitoes. Pools should be drained, or, if this is not feasible, may be treated with kerosene; or small fish, which feed upon the larve, may be introduced into the mosquito-breeding ponds. The quickest and most satisfactory way to destroy larve and pupz is by the formation of the kerosene film upon the water’s surface. The oil is best applied for this purpose as a spray, or, if but a small area is to be treated, it may be thrown upon the surface and the water then vigorously stirred. About one ounce of kerosene to fifteen square feet of water surface will be sufficient, and this application should be repeated at intervals of about three weeks.
Such measures are directed only against local species, and, essentially, there must be community action for it to be effective. Migratory forms, such as are bred in the marshes near our coasts, cannot thus be reached, their eradication constituting a problem demanding state control.
For indoor protection in mosquito-infested districts, screening is of course essential. In spite of the most thorough screening, however, mosquitoes will enter in various ways, as through opening doors and upon the clothing of persons passing in. As remedies against those which have gained access to houses various kinds of repellents are used. Burn- ing pyrethrum powder will often rid a room of mosquitoes, a convenient method being to sprinkle the powder upon a heated shovel; or small cones may be molded from the dampened powder and, after drying, burned. Oil of pennyroyal or citronella applied to handkerchiefs or lightly touched to the hands and face, though objectionable to some, will usually insure a peaceful night against the pests.
Famizy II. Simvtup#
Diptera (p. 23). The flies of this family are known as black flies, black gnats, or buffalo gnats, the latter name derived from their peculiar humpback appearance. They are dark colored, with short thick body,
32 PARASITES OF THE DOMESTIC ANIMALS
short eleven-segmented antennz, no single eyes, broad wings, and stout legs. Only the females are provided with piercing mouth parts.
The larvee, so far as known, are aquatic. The eggs are deposited in a compact layer upon some object, usually rock, near the surface of a flowing stream. Upon hatching the larve drop into the stream and live attached to sticks, stones, or other objects under the surface of swiftly running water. They may detach themselves and move about in a looping manner similar to that of the measuring worm, or they may be carried by the current for considerable distances. Respiration is carried on by gill-like processes.
SImMuLIUM PECUARUM
The Southern Buffalo Gnat (Fig. 17). Simuliide (p. 31). The adult female is nearly a quarter of an inch in length, the male somewhat smaller. The color of the body is black, and it is covered with light brown hairs which are arranged upon the thorax in such a manner as to give a longitudinal striped appearance, the abdomen showing upon its dorsal side a broad grayish stripe widening out toward the abdominal apex. The male notably differs from the female in that the eyes are much larger and join each other in the middle line. The individual facets on the upper part of the eye are considerably larger than those of the female.
The larva (Fig. 18) agrees in gen- eral appearance with that of other species of Simulium. It is about three-eighths of an inch in length, twelve-segmented, somewhat con- ee stricted in the middle, enlarging to- Beare ee Oren a ward both ends. The posterior end Bureau of Entomology, Dept. of Agr.). 18 the larger and is somewhat club-
shaped. In addition to the mouth, the head possesses two fan-shaped bodies which are prehensile in func- tion. On the top of the last abdominal segment there are rows of hooklets, while in the vicinity of the rectum are organs of respiration consisting of three tentacles to which the large trachee lead.
The pupa (Fig. 19) has a peculiar tuft of respiratory filaments starting from each side of the thorax. The upper portion of the pupal case is open, exposing the head and permitting the respiratory filaments to
MOSQUITOES AND GNATS
33
have free access to the water. The pupa is firmly attached to sticks, leaves, or other submerged objects. On emerging from the pupal case
the fly at once rises to the surface and, expanding its wings as it runs upon the water for a short distance, flies swiftly away.
Occurrence and Effect.—The buffalo gnat has been found in Alaska and throughout the Eastern United States, but appears in greatest numbers in the South, especially about the mouths of rivers and creeks. During the worst years the whole of the Lower Mississippi Valley as far north as St. Louis may be invaded.
The attacks by swarms of this bloodthirsty and vic- iously active insect upon southern live stock is a source of serious injury and loss. Cattle and horses will mani- fest the presence of the swarms by frantic efforts to de- fend against the attack, cattle rushing wildly about and horses and mules trying to escape by running away. The most destructive raids of the fly usually occur in the months of March and April. They are exceedingly swift in their flight, darting at their victims in search of a suitable place to draw blood, and in their bite instilling a poison. Many animals die from ex- haustion, combined with the toxic effects of the poison from the bites. Bronchitis and pneumonia, resulting
Fig. 18. — Si- mulium pecua- rum, larva—en- larged (after Os- born, Bul. No. 5, Bureau of Ento- mology, Dept. of Agr.).
Fic. 19.—Simulium pecuarum, pupa—en- larged (after Osborn, Bul. No. 5, Bureau of Entomology, Dept. of Agr.).
from the inhalation of large numbers of the insects from which the exhausted animal becomes totally unable to defend itself, may also contribute to the conditions leading to its miserable death. Control.—Outbreaks in heavily infested districts may be lessened in frequency and severity by the clearing out of logs and other débris in the beds of streams, thus reducing the number of objects for: attachment of the larve. Unlike those of the mos- quito, the larve of Simulium thrive best in swiftly running and well aérated water, therefore the re-
moval of any submerged object causing shallow and swiftly moving water reduces the possibilities for breeding at this point. Protection.—The black gnat dislikes smoke, therefore, as prevention against its attacks in fields and barnyards, the maintenance of smudges is of value. Other repellents, such as fish oil, oil of tar, or other oleagin- ous and resinous substances, either singly or in combination, are applied to the surface of the body, affording a measure of protection
34 PARASITES OF THE DOMESTIC ANIMALS
from attacking swarms. The most effectual protective measure is the sheltering of animals in a cool dark stable during the hours of the day when the swarms are most active.
Treatment.—Animals weakened by the bites may be given a dif- fusive stimulant and have the parts locally treated with a solution of bicarbonate of soda or ammonia water.
CHAPTER V THE. FLIES
Family III. Tabanide.—Diptera (p. 23). This family includes the so-called horseflies or gadflies. The head and eyes are large, the latter often of a brilliant color. The third segment of the antenne has four to eight rings. The proboscis of the female is adapted for piercing the skin of animals. The males do not attack animals; their mouth parts are less powerful than those of the females and are adapted for feeding upon the juices of plants. The body has fine hairs; there are no bristles. The flight is strong and swift and is accompanied with a tormenting buzzing noise.
The eggs of Tabanide are deposited in masses upon vegetation grow- ing in wet marshy ground. The larve are carnivorous and are aquatic or live in moist earth.
TaBANus ATRATUS
Tabanide (p. 35). This is the common large black horsefly, having a wide distribution in the United States. It is one of the larger species of the family, measuring an inch or more in length and having a body so uniformily black as to attract attention even when it is upon the wing (Fig. 20).
The eggs are deposited in masses, usually upon the stems of plants or grasses growing in the vicinity of water. In about seven to ten days there is hatched a large cylindrical Jarva which tapers to a point at both ends and has an integument that is somewhat transparent (Fig. 20, a). At this stage it lives mostly in moist earth into which it burrows actively, feeding mainly upon worms and the larve of other insects. While the period of larval life is long, in some observed cases lasting several months. to a year, the stage of the pupa (Fig. 20, b) is short, the fly emerging from its case after a few days of pupation. It is probable that the broods are carried over the winter in the larval stage.
Effect.—The black horsefly is common throughout the summer months, attacking cattle and horses usually in the open sunny pasture, and inflicting with its long piercing mouth parts a painful wound. For- tunately it does not attack in swarms as does the buffalo gnat, nor does it instill with its bite as much poison. There is evidence of the severity of its wound, however, in the drop of blood which wells up from the seat of puncture after the insect has left its victim. While there is little
36 PARASITES OF THE DOMESTIC ANIMALS
after-effect from the bites of these flies they are a source of much tor- ment to live stock, not only in the pain produced by their punctures, but in their peculiar buzzing, which often terrorizes nervous animals, their frantic and heed- less efforts to escape not infrequently — resulting in injury.
There can be no doubt that the Taba- nidz are concerned in the transmission of cer- tain blood diseases of live stock. It is signif- icant as to their possi- bilities as carriers of anthrax that their at- tack seems to be more commonly directed against cattle than
Fig. 20.—Tabanus atratus: a, larva; b, pupa; c, adult horses. (after Osborn, from Riley, Bul. No. 5, Bureau of Ento- Protection. — Little mology, Dept. of Agr.). x ;
can be done toward repelling the attacks of the flies. Horses at work are protected in a measure by covering them with nets. Where the flies are numerous and especially tormenting it is advisable to remove pasturing animals to a well-shaded retreat during the warmer and sunnier parts of the day.
Tapanus LINEOLA
Tabanide (p. 35)—The Green-head Horsefly (Fig. 21). This is the most widely distributed species in North America. It is about five- eighths of an inch in length. Eyes large and bril- liant green, abdomen brown, with a conspicuous grayish line running longitudinally on its dorsal side. It is from this marking that its specific name is derived, while the peculiar coloring of the eyes gives to it the common name ‘‘Green-head.”
The oval, larval, and pupal stages are passed one a RE ase
after Osborn} in moist places, and in other respects the life cycle from Packard, Bul. No.5, is similar to that of Tabanus atratus, though the aes Entomology, larval period is probably not so long. ae ai
The Green-heads appear in especially large numbers in marshy dis- tricts during the brightest and hottest days of the summer. They attack in greater numbers than the Black Horseflies, and, especially
THE FLIES 37
during warm and sunny weather, their harassing bites cause much torture to horses and cattle. They do not fly in cloudy weather, and they perish with the frosts of early autumn.
Famity IV. Muscip#
Diptera (p. 23).—These flies are small to moderately large, with bodies thinly covered with hairs or bare. The bristles of antenn# are feathery. The abdomen is four-segmented and smooth except for bristles near the tip.
The larve are apodal maggots, feeding upon decaying animal or veg- etable matter.
Musca Domestica
The common house fly (Fig. 8). Muscide (p. 37).—The mature in- sect is one-fourth to five-sixteenths of an inch in length; dorsal region of thorax grayish in color and bearing four longitudinal stripes; abdomen yellowish. The mouth parts are trumpet-shaped, adapted for sucking up liquids but not for piercing.
Life History.—In about ten days after emerging from the pupal case the female fly seeks suitable material upon which to deposit her eggs. This may be any decaying vegetable matter, though usually horse stable manure. About one hundred eggs are deposited at each laying, of which there are several at intervals of three to five days. In eight to twenty-four hours a white, footless larva is hatched. After five days to one week of feeding and and growing, during which period it undergoes two molts, the larva enters the pupal stage, the larval skin serving as its puparium. Before entering this stage the maggot may crawl away from its breeding place and burrow for a short distance into the adjacent ground, or find lodgment under a board, stone, or dried crust of manure. The stage of pupation lasts from five days to one week, and at its termination the adult fly emerges.
According to the longer periods given, the time required for develop- ment from the egg to the imago is fifteen days. This time, however, is greatly influenced by temperature, under the most favorable conditions of which the period for complete metamorphosis may be reduced to ten days; a fact always to be reckoned with in dealing with control of the fly through the regular and systematic removal of stable manure or other material which may serve as its breeding bed.
In the warm midsummer season adult flies may live for six to eight weeks, though it is probable that the average period will not exceed thirty days. They may survive the winter in a state of hibernation, seeking their retreats in the late fall months, and coming forth with the warm days of early spring to crawl upon the windows as they seek the warm sunlight or exit from houses.
38 PARASITES OF THE DOMESTIC ANIMALS
Habits and Relation to Disease.—While, so far as known, the house fly is not an essential host to pathogenic organisms of man and the mammalian domesticated animals, it is, by its structure and filthy habits of feeding, one of the most dangerous of disease-transmitting insects. Omniverous in habit, it will feed upon decaying vegetable and putrid animal matter, excrement, vomit, sputum, or other revoltingly filthy material. Direct from such sources of infection it may pass to the food upon our tables to which it is equally attracted, -leaving a trail of contamination wherever it may drag its filthy parts.
From the viewpoint of the bacteriologist it would seem superfluous to discuss the house fly as a carrier of disease-producing bacteria. The form of its proboscis, habit of regurgitating its food, its six bristly feet (Fig. 8), each terminated by a sponge-like structure secreting a sticky substance, together with the vile material which it visits, make it both by structure and habit an ideal transmitter of such infectious diseases as typhoid fever, dysentery, cholera, glanders, anthrax, and ophthalmia. Furthermore, positive evidence of the degree to which this insect is a carrier of bacteria has been well set forth by laboratory experiment.
Control.—As a widely disseminated menace to public health the house fly presents a problem that can only be successfully dealt with by community action. The measures taken should look to control rather than elimination, the latter, however desirable, being scarcely possible under present conditions. While it prefers horse manure, it is known that almost any fermenting material will serve as a breeding place, and it therefore follows that, in order to successfully combat this pest through its sources of propagation, all such material must be systematically re- moved, screened off, or so treated as to render it unsuitable for the development of the larve. Manure should be removed at least once a week, and if possible at once spread upon the fields. Kitchen garbage should be likewise removed, and in the meantime kept in tightly closed receptacles. Access of flies to the vaults of outhouses can be prevented by their proper structure and screening.
Protection.—As to measures of protection to the household against flies, there is little to be said that is not of common knowledge. The first of these to be mentioned is the thorough screening of doors and windows. Kitchens being especially attractive to flies, they should be doubly protected by screening the back porch, the screen doors at these locations being well fitting and made to withstand their frequent use. Flies that have gained entrance are best gotten rid of by burning pyre- thrum powder. A good method for the treatment of a room is to sprinkle the powder upon a hot shovel after first closing the doors and windows; if the kitchen, the powder may be sprinkled over the stove. It is best applied at night, leaving the room tightly closed. In the morning the flies will be found lying about dead or stupefied, when they may be
THE FLIES 39
swept up and burned. The use of poisonous liquids set around in dishes has but little efficacy and for other reasons is not to be recommended. Sticky fly paper, to be most effectual, should be placed in parts of the room where there is most sunlight, as in the vicinity of windows.
In this connection it should be borne in mind that adult house flies and their allies seek the light, while their larve avoid it, characteristics referred to in the first case as light positive and in the second as light negative. This habit as to light is to be reckoned with and taken ad- vantage of in measures looking to fly control.
STOMOXYS CALCITRANS
Stromoxys stabulans. Stable fly; stinging fly. Muscide (p. 37). About the size of the house fly. The color is brownish gray; proboscis black, slender, bent near its base, and extending forward from the head, fitted for piercing. The thorax bears four longi- tudinal stripes which may be more or less broken. The abdomen is stout, grayish, and spotted dor- sally. The wings hyaline, and when at rest. widely spread apart at the tips. The fly rests with its head well elevated and with wings sloping later- ally downward and outward (Fig. 22).
The eggs are about one mm. in length, curved on one side, on the opposite side straight and grooved. The larve resemble those of the house fly. They may be differentiated by the posterior stigmal plates, which in the larve of the house fly are large, irregularly oval, and close together, while in Stomoxys they are smaller, round or triangular, and much farther apart.
Life History.—The life-cycle of the stable fly is considerably longer than that of the house fly; like the latter it breeds in horse manure, but not to the same extent. Manure well mixed with straw is that most sought. Ideal for the deposition of its eggs are damp and fermenting collections of such material as cut grass, alfalfa, hay, grain, or piles of weeds. The eggs are deposited deep into the fermenting mass, and, under favorable conditions of temperature, will incubate in about three days. The larve are active feeders and complete their growth in from twelve to thirty days. As in related flies, the puparium is formed by the hardening of the last larval skin. The duration of the pupal stage will again vary according to weather, lasting from six to twenty days, or, if cool, it may be much longer. About twelve days may be taken as an average period. The time required for complete development may accordingly be set down as from twenty-five to thirty days under ordinarily favorable conditions. It is probable that the species is car- ried over the winter months in our Northern States in the larval and
Fig. 22.—Stomoxys cal- citrans, enlarged.
40 PARASITES OF THE DOMESTIC ANIMALS
pupal stages. Development with the appearance of adult flies will occur in warm stables during this season.
Occurrence and Effect.—The stable fly is of world-wide distribution, and is commonly mistaken for the house fly, the term ‘‘biting house fly”’ being often applied to it from its habit of entering our houses during damp, rainy weather and in the cooler days of early autumn. It may quickly be distinguished from the common house fly, however, by its elevated head when at rest, its protruding, bayonet-like proboscis, and its wings, which are widely spread apart at the tips.
Though commonly called the stable fly, Stomoxys is found in far less numbers about stables than is the house fly, and, as it will not visit such filth as does the latter, it is not such an offender against the cleanliness of dairy and other food products. Both sexes of Stomoxys, however, are vicious blood-suckers, and their bite is especially a source of torture to thin-skinned, sensitive animals. Typically an out-of-door fly, it is most likely to enter stables in the cooler days of late summer or early autumn when it will attack horses and cattle, attaching itself by prefer- ence upon the legs. Their sharp sting is manifested by the stamping, kicking, and general restlessness of the victims. The punctures are often followed by the formation of papules which may coalesce and rupture, leaving a scaly, more or less thickened skin with hairs scant, lusterless, and erect. To the dairy they are a source of loss in milk production through the worry and unrest caused by their attacks.
Relation to Disease.—The possibilities of the stomoxys fly as a disseminator of infectious diseases have in recent years received con- siderable attention. Its habit of visiting a number of hosts before becoming engorged with blood, together with its deep puncture, war- rants us in charging against this species possibilities in the transmission of anthrax in cattle and glanders in horses. By some authors it is re- garded as a carrier of the trypanosome (Trypanosoma evanst) which produces surra of horses. Of this, however, there is no conclusive experi-
“mental.evidence. As to the responsibility of the stable fly for the spread
of infantile paralysis, it will be sufficient here to quote Riley and Johann- sen, who, after reviewing the evidence, thus state their conclusions (1915): “‘The evidence at hand to date indicates that acute anterior poliomyelitis, or infantile paralysis, is transmitted by contact with infected persons. Under certain conditions insects may be agents in spreading the disease, but their réle is a subordinate one.”
Control.—Control measures consist in removing materials which afford favorable breeding places for the fly. Collections of moist and fermenting feed material, such as have been mentioned, should be re- moved and scattered in a layer sufficiently thin to insure thorough drying. It will then be unsuitable for the development of stomoxys larve, as they require considerable moisture. Manure in which there is
THE FLIES 41
mixed considerable straw affords a favorable medium for the propaga- tion of this fly,—a further reason for its systematic removal to be at once spread upon the fields, as stated in control measures for the house fly. It should be borne in mind, however, that stables are not predominant as breeding places of the fly under consideration, as is the case with the house fly. Stomoxys is attracted to stables because the animals from which it obtains its meal of blood are contained there. The favorite material for the deposition of its eggs is likely to be found elsewhere. These flies like the open, and districts far from stables may be overridden with them.
Protection.—Little can be done in the way of direct protection of live stock against the attacks of stable flies beyond thorough screening, the effectiveness of which is much lessened by the frequent opening of doors customary about stables. Means of keeping them out should be especially looked to in cloudy, damp weather, and in the cool mornings of early autumn, at which times they are most likely to seek the interior of stables and houses.
Lyprrosta [RRITANS
Hematobia serrata.—The horn fly (Fig. 23). Muscide (p. 37). About half as large as the house fly and like it in shape and color. The mouth parts are adapted for piercing and sucking blood, but differ from those of the stable fly in that the palpi are almost as long as the proboscis and are slightly spatulate.
The eggs (Fig. 23, a) are about 1.25 mm. in length, irregularly oval, and reddish brown in color. They are deposited in the fresh dung of cattle, and, under favorable conditions of temperature, will hatch in about twenty-four hours.
Life History.—Newly hatched larve are about 2.5 mm. in length, and pure white. When full grown they are about 7 mm. in length and somewhat darker in color. The larve burrow into the dung and reach their full growth in about four days (Fig. 23, b). When ready to trans- form into the pupal stage the larve descend into the dryer parts of the dung, or for a short distance into the ground beneath it. The puparium (Fig. 23, c) is about 4.5 mm. in length, irregularly ellipsoidal, and dark brown in color. The pupal stage occupies from five to ten days, therefore the time for full development from the deposition of the eggs will be, according to the above, from ten to fifteen days.
Occurrence and Habits.—The horn fly is an importation from Europe, making its first appearance in the vicinity of Philadelphia about the year 1886. It was first noticed as a pest to cattle in this country in 1887, from which time it has spread rapidly and at present is found in practically all parts of the United States and the greater part of Canada.
The popular name “horn fly” is derived from the habit peculiar to
42 PARASITES OF THE DOMESTIC ANIMALS
this species of clustering about the base of the horn, though this only occurs when they are quite abundant. Their purpose in collecting here seems to be for rest in a location where they are not liable to be dis- turbed. There is a somewhat prevalent belief that the flies damage the horn by eating into it, depositing eggs, and developing maggots which may penetrate to deeper structures, etc. This is a popular error for which there is no foundation, for, beyond ‘‘fly specking,”’ it has not been observed that the flies do any injury to the horn.
Field study will show that this insect assumes two characteristic posi- tions. In the resting position, as they are found when upon the horns,
Fic. 23,—Lyperosia irritans: a, egg; b, larva; c, puparium; d, adult in biting position—all enlarged (after Osborn, from Riley and Howard, Bul. No. 5, Bu- reau of Entomology, Dept. of Agr.).
the wings are held nearly flat down the back, overlapping at their bases and moderately diverging at their tips. The proboscis is extended for- ward, and the legs are not widely spread. When active and feeding, on the other hand, the wings are slightly elevated and held almost at right angles to the body, while the legs are spread. The proboscis is nearly perpendicular in position, and penetrates the skin of the animal at- tacked. To secure this position it works its way to the skin, and is usually observed more or less covered by the hairs. In damp, rainy weather they may be noticed as particularly abundant beneath the hairs of the ventral surface of the body.
Effect.—Horn flies appear early in May and become most abundant in July and August. With the coming of cold weather they disappear,
THE FLIES 43
their full period depending upon season and latitude. During the time of their activity they are a veritable pest to cattle, causing interference with their grazing and disturbance of their rest, with consequent un- thrift and serious loss in productiveness. Horses do not escape their annoyance, but cattle seem to be the special object of their attack. Though the damage done is chiefly through their torment, the con- siderable amount of blood extracted from the animal by the large swarms which feed upon it must seriously contribute to the weakening effects. Further, as in all blood-sucking Diptera visiting cattle, we are justified in inferring that this fly may be a transmitter of infectious blood diseases, such as anthrax, though as to this there has as yet been little if any investigation.
Control.—In control measures two lines of procedure should be fol- lowed, one Jooking to prevention of multiplication, the other directly protecting cattle from attack. Of these the former is most effective and involves such treatment of breeding places as will prevent larval develop- ment. As eggs are deposited in fresh dung, which must remain moist for the proper nourishment of the hatched larve, any treatment of the droppings which will cause them to rapidly dry out will prevent or greatly inhibit larval development. Scattering or thinly spreading this manure, as may be done by a rake or by drawing brush across the fields, will accomplish this; the latter method, more economical in time and labor, is best adapted for large pasture areas. Hogs running with cattle will serve to scatter the manure to a large extent. The use of lime, which may be applied by simply throwing it over the droppings in the pasture, is very effective in destroying the larve. While piles of cow manure, especially those containing considerable straw, afford good breeding places for the stable fly, the horn fly will not seek this material to any great extent for the deposition of its eggs.
Protection.—For the direct protection of cattle a number of oleagin- nous repellents are recommended. A mixture of fish oil and tar, equal parts, applied to the regions most attacked, is one in general use. Almost anv oily or greasy substance is of value, though causing the animal to become somewhat unsightly from adhering collections of dust and dirt. Sprays of kerosene emulsion (page 48) may be used with advantage, though the effectiveness of such treatment is very transient. The following mixture is recommended by the Kansas Experiment Station: resin (pulverized), one part; shaved soap, one part; water, one-half part; fish oil, one part; oil of tar, one part; kerosene, one part; water, three parts. The resin, soap, fish oil, and one-half part water are boiled to- gether until the resin is dissolved, then the three parts water are added, and finally the kerosene and oil of tar. The mixture should be thor- oughly stirred and boiled for fifteen minutes. This preparation when cool and applied as a spray will act as an effective repellent for twenty-
44 PARASITES OF THE DOMESTIC ANIMALS
four to forty-eight hours. It is necessary, therefore, to regularly repeat the application if the animals are to be continuously protected. Re- pelling agents are best applied in the evening when cattle are stabled or yarded.
TsETSE FLIES
Genus Glossina.—Muscide (p. 37). The tsetse flies (Fig. 24) are about the size of house flies, or may be somewhat larger. The general color is light brown. When at rest the proboscis projects in front of the head. At the base of the proboscis is a bulbous enlargement, arista
Fic. 24.—Tsetse fly.
plumose above. The resting wings are folded scissors-like over the back.
These flies are found only in certain areas in Africa.
Glossina Palpalis.—Glossina (p. 44). This species is 8 to 9 mm. (5/16 to 3/8 of an inch) in length. The color is brown dusted with gray. The antenne are black. All segments in the hind tarsi are black. The fourth and fifth segments of the fore tarsi are black. The halteres are white.
Glossina Morsitans.—Glossina (p. 44). About the same size and color as G. palpalis. The antenne are dark. The first.three segments of the hind tarsi are yellow, the fourth and fifth segments black. The fourth and fifth segments of the first and second pairs of tarsi are black.
Glossina longipalpis is a species which in characteristics and distribu- tion is almost identical with G. morsitans.
Breeding Habits and Habitat.—The Glossina deposit hatched larve among roots of tropical vegetation. When deposited the larve are well
THE FLIES 45
advanced and within a few hours enter upon the pupal stage which re- quires from six to eight weeks. Occurring only in Africa, they are most abundant in heavily wooded districts penetrated by water courses. Both sexes are blood-sucking, and it is in such locations that they are most likely to find the wild animals upon which they feed. Relationship to Trypanosomiasis.—As transmitters of trypanoso- miasis to man and domestic animals, tsetse flies may be regarded as the world’s most dangerous insects. The first observation of trypanosomes in the blood of mammals was made by Lewis, who in 1877 described a trypanosome (Trypanosoma lewisi) of the blood of a rat. Three years later another trypanosome (T. evans) was studied as the cause of surra in horses. When Bruce in 1894 demonstrated the relationship between tsetse fly disease of horses in Africa, the cause of which was unknown, and nagana, trypanosomes received much more attention as to their pathogenic importance. The further investigations of Bruce as to the part played by the tsetse fly in the transmission of this disease are best given in his own account, from which the following is an excerpt: “When it was once established that the two diseases were the same, experiments were made to find out how the animals became infected, whether the fly was the carrier or the mere concomitant of the low-lying, unhealthy district, and, if a carrier, if it was the only carrier of the disease from sick to healthy animals. Horses taken down into the fly country, and not allowed to feed or drink there, took the disease. Bundles of grass and supplies of water, brought from the most deadly parts of the fly country to the top of Ubombo and there used for fodder for healthy horses failed to convey the disease. Tsetse flies caught in the low country and kept in cages on top of the mountain, when fed on affected animals, were capable of giving rise to the disease in healthy animals up to forty- eight hours after feeding. Tsetse flies brought up from the low country and placed straight way upon healthy animals were also found to give rise to the disease. The flies were never found to retain the power of infection for more than forty-eight hours after they had fed upon a sick animal, so that if wild tsetse flies were brought up from the low country, kept without food for three days, and then fed on a healthy dog, they never gave rise to the disease. In this way it was proved that the tsetse fly, and it alone, was the carrier of nagana. Then the question arose as to where the tsetse flies obtained the trypanosomes. The flies lived among the wild animals, such as buffaloes, koodoos, and other species of antelopes, and naturally fed on them. It seemed that, in all probability, the reservoir of the disease was to be found in the wild animals. There- fore, all the different species of wild animals obtainable were examined both by the injection of their blood into healthy susceptible animals, and also by direct microscopic examination of the blood itself. In this way it was discovered that many of the wild animals harbored this
46 PARASITES OF THE DOMESTIC ANIMALS
trypanosome in their blood. The parasites were never numerous, so that it was only after a long search that they could be discovered by the microscope alone. The wild animals did not seem to be affected by the trypanosomes in any way; they showed no signs or symptoms of the disease, and it, therefore, appeared probable that the trypanosomes lived in their blood as harmless guests, just as the trypanosome of the rat lives in the blood of that animal.”
As Trypanosoma brucei is now known to be the organism causing the fatal nagana of horses and mules of Africa, so 7’. gambiense is known to be the cause of sleeping sickness of man. The relationship of the tsetse fly to human trypanosomiasis was shown in a way very similar to that by which Bruce reached his conclusions. While the tsetse species Glossina morsitans and G. longipalpis are especially concerned in the transmission of nagana, and G. palpalis likewise related to sleeping sick- ness, it has been shown by students in the field of protozoélogy that not only biting flies, but mosquitoes, lice, and leeches may carry trypano- somes from one vertebrate host to another.
Experiment has shown that the trypanosomes adhering to the pro- boscis of the biting fly after it has fed upon the blood of an infected animal rapidly lose their vitality, becoming sufficiently attenuated within forty-eight hours to be noninfective. The fly, therefore, can only inoculate mechanically, that is by the puncture of its soiled pro- boscis, within a few hours after it has become a carrier of the infecting organism. It is now known, however, that trypanosomes taken into the stomach of the fly with its meal of blood pass through a metamor- phosis involving sexual forms, and that at the end of about twenty-eight days the fly may again become infective. At this time the parasites have reached the salivary glands and here they remain during the re- mainder of the life of the fly. How long such a fly may retain its power to infect is vet a question, though it has been found by the Sleeping Sickness Commission to be at least three months. The duration of the life of the tsetse fly has only been observed upon specimens in captivity, but it is probable that it is about four to six months.
Control.—Measures looking to the control of the breeding of the flies are limited practically to exclusion owing to the fact that the larval period is passed within the body of the female, hence offers no opportu- nity for attack through sources of larval food supply. The fact that tsetse flies seek the vicinity of water courses surrounded by wooded areas may be taken advantage of in excluding them from locations of settlement. With a view to this it has been recommended that clearings be made over an area of six hundred to eight hundred yards at some distance from streams of water, the water supply being obtained from wells. The difficulties presented, however, in the control of the fly are numerous and in many features seem unsurmountable. The ultimate
THE FLIES AT
solution of the problem probably lies in immunization against the tsetse fly diseases, as to which little progress has yet been made.
Famity V. Hippoposcip®
Diptera (p. 23).—The body is flattened. Wings are present or absent. The wing veins are crowded toward the anterior margin. The head is sunk into an emargination of the thorax; the antenne inserted in pits near mouth; mouth parts adapted for piercing and sucking blood. The legs are stout, terminated by strong claws. The abdomen is large and sacular with segments indistinct.
The Hippoboscide are pupiparous, the eggs being hatched and nearly the whole of the larval stage passed within the body of the parent. The larve are extruded only when nearly ready to transform into pupe.
All are parasitic upon birds and mammals. . Hippobosca equina is a winged species occurring upon the horse, and known in England as the forest fly.
MELOPHAGUS OVINUS
The sheep “tick.’”—Hippoboscide (p. 47). Three-sixteenths to one- quarter of an inch in length. The color reddish or grayish brown. The wings and halteres are ab- sent. The head is small and sunken into the thorax; ab- domen large, sac-like, and covered with short spines (Fig. 25).
Life History.— Matured lar- ve are extruded from the body of the female and at once enter upon their pupation, the red- dish brown pup adhering to the wool fibers. The pupal stage occupies three to six weeks according to season and temperature, the shorter period occurring during the summer. At sexual maturity the deposi- tion of pupz begins, each fe- male depositing from eight to ten. Probably the life of the oA tick will not exceed four to five Fic. 25.—Melophagus ovinus (from photo- ee graph of mounted specimen, by Hoedt).
Occurrence.—The sheep tick is distributed over all parts of the world where sheep are kept. Its parasitism is continuous, the pupiparous
48 PARASITES OF THE DOMESTIC ANIMALS
habit of bringing forth its young adapting it to spend its whole life upon the host from which it never migrates unless to attach to another animal of the same species. It is probable that this migration occurs principally at the time of shearing when the ticks leave the sheared sheep and crawl upon the lambs. Off the host the ticks will not survive longer than a few days, probably all will be dead within a week.
Effect.—All breeds of sheep are alike subject to attack, the presence of the “tick,” or “louse,” as it is commonly called, and the injury which it causes, being a matter of common knowledge to sheep breeders. Sheep are not materially affected by a few, but if in larger numbers, their presence will be manifested by rubbing, scratching, and biting at the fleece. Loss of flesh and general unthriftiness will occur in badly in- fested animals. Where the ticks are prevalent lambs may be attacked by large numbers at shearing time, in which condition many will die unless promptly relieved’
Treatment.—In the winter months, when the long wool will not permit of other treatment, the ticks may be greatly reduced in number by the use of pyrethrum powder which should be freely blown deep into and upon the fleece over all parts of the body. The most effectual treat- ment is best applied after shearing and consists of the application by dipping or as a wash of such remedies as creolin, zenolium, lysol, or cresol, used in two to three per cent. strength. Decoction of tobacco, in strength of three to four per cent. is also used, but, to avoid danger of nicotine poisoning, should not be applied to all parts of the body at once. Kerosene emulsion, which has a wide range of usefulness in the treat- ment of external parasites, is another of the numerous dips resorted to in this connection. The emulsion may be made either with milk or soap according to the following formule:
Milk emulsion—To one part milk add two parts kerosene and churn by a force pump or by other means of agitation. Dilute the resulting emulsion with eight to ten times its bulk of water.
Soap emulsion.—Dissolve one-half a pound of hard soap in one gallon of hot water and, while still at near boiling point, add two gallons of kerosene. Emulsify by use of force pump or other means of agitation. Dilute one part emulsion with eight or ten parts water.
These emulsions 'may be used in the proportions given as a spray, wash, or dip. ‘
None of these dips will kill the pupa, and, therefore, keeping in mind the life history of the parasite, the treatment should be re- peated in about twenty-four days. If the dipping has been done in the cooler weather of autumn, this interval should be accordingly prolonged.
As the movement of the ticks from the sheep to the lambs takes place principally at the time of shearing when the insects are removed from
THE FLIES 49
their host with the fleece, it is well at this time to keep the lambs at some distance from the stored wool. This precaution should be ob- served for at least a week from the time of shearing, at the termination of which period the ticks which have been removed with the wool will be dead.
CHAPTER VI DIPTEROUS LARVA
Flesh flies, blowflies, botflies—The larve of these flies produce a form of parasitism to which the term myasis (also myiasis, and myiosis) is applied. Various forms of myasis are recognized according to the location of the larve, as cutaneous, muscular, nasal, gastric, and intes- tinal. With certain species, as those of the family (stride, or true botflies, the larval parasitism is obligate upon or within a living host animal, while the larvee of the flesh and blowflies of the family Muscidze may attack either living or dead, usually decomposing, tissue.
Curysomy1A MAcELLARIA
Compsomyia macellaria; Cochliomyia macellaria, Screw worm fly.— Muscide (p. 37). Three-eighths to half an inch in length; color bluish green with metallic reflections. There are three longitudinal black stripes upon the thorax. The head is reddish or yellowish brown; thorax and abdomen covered with stiff black hairs (Fig. 26).
The eggs are about 1 mm. in length, white and cylindrical. They are deposited in masses of three hundred to four hundred upon dead and decaying flesh and upon wounds, sores, or within the nostrils or other natural mucous openings of man and lower animals. Hatching may occur in from one to twelve hours from the time the eggs are deposited.
The larve are white, apodal, slender, and quite active. The head and segments are provided with spines which facilitate their burrowing into the living or putrefying flesh upon which they feed, a habit which gives to the mature insect its common name of screw worm fly. Under most favorable conditions the full larval growth is reached in three days, at which time they may be half an inch or more in length. When mature they leave the flesh upon which they have been feeding and bury them- selves in the earth near by, in which location they enter upon pupation.
The pupe are 6 to 9 mm. in length, somewhat barrel-shaped, and dark brown in color. The pupal stage may last from six to twelve days.
Occurrence and Effect.—The screw worm fly is widely distributed, being found throughout North and South America. In the United States it is especially abundant in the South, where it is responsible for the most serious cases of human myasis occurring in this country. It begins to attack in June, but has its greatest period of activity in the
DIPTEROUS LARVA 51
three months which follow. In its attacks upon man it usually deposits its eggs in the nostrils or mouth while the individual is sleeping. It is especially attracted if the parts are unclean, as from the discharge of nasal catarrh or collections of vomit about the lips. Persons in a drunken stupor are especially liable to attack. For the same reason open sores contaminated by collections of pus or blood are equally attractive to it.
The fly’s greatest injury as a pest to domestic animals in the United States occurs in the Southwest, where cattle are the greatest sufferers from its ravages. In-these animals the flies are attracted to wounds of operations, such as dehorning, branding, castrating, etc., and to injuries such as may result from hooking or barbed wire. In fact any open wound or exposed mucous mem- brane, especially if soiled with an odorous discharge, is a favorite seat of attack.
Upon hatching, the larve at once proceed to attack the tissues and may rapidly produce a serious de- struction and mutilation. They grow rapidly as they consume the tissues adjacent to them, and in locations, as parts of the limbs where there is little fleshy covering, the bones may be laid bare.
Protection.—As most of the fatal Fie. 26—Compsomyia macellaria—en- cases of myasis 1n man from this larged (after Osborn, from Francis, Bul. cause are due to deposition of eggs No. 5, Bureau of Entomology, U. S. Dept. in the nostrils while the person is eer sleeping, the first measure of precaution is to protect from attack by the use of netting. Those sleeping out of doors in infested regions are most exposed, but sleeping rooms should also be thoroughly screened. Open sores and wounds should of course be kept free from collecting discharge and covered with clean, dry dressing.. The same precautions as to cleanliness of wounds and exposed mucous membranes applies to domes- tic animals. The vulve of cows recently fresh, especially if there has been a retention of the placenta, and the navels of calves offer favorite points for attack and should particularly be guarded.
Treatment.— Where sores and exposed mucous membranes have already become infested with worms a disinfecting wash, such as a one to three per cent. solution of carbolic acid, should be used. For injection into regions where the maggots have penetrated, the injection of carbolic acid or creolin in about five per cent. strength will destroy worms with which it comes in contact. Chloroform diluted to a strength of about
52 PARASITES OF THE DOMESTIC ANIMALS
twenty per cent. is also recommended for this purpose. An ordinary machinist’s oiler affords a practical method of applying such agents. It has the advantage of deep application without waste of the material. For deeply infested wounds a final packing of oakum and oil of tar should be applied, and this should be covered by a protective dressing of tar and oakum as a prevention from further attack.
SARCOPHAGA SARRACENIA
A flesh fly—Muscide (p. 37). In markings somewhat similar to the house fly, but considerably larger. The general color is light gray; eyes reddish brown. Body spiny.
The female deposits larvee upon fresh meat, or in the wounds of living animals. Under favorable conditions the larval stage is completed in : about six days. The : 3 mature larve crawl to : Se g a convenient shelter ap E “ where they undergo a Fig. 27.Metamorphosis of the flesh fly (Sarcophaga): pupation from which
a, eggs:b , young larve just hatched; c, d, full-grown larve; the adults issue in from e, pupa; f, imago (after Orton, by Dodge; Copyright, 1894, twelve to fourteen
by Harper & Brothers). days (Fig. 27).
Protection.—The flesh flies are of world-wide distribution, and are of most importance as they affect fresh meats in the household or meats in storage. As a protection in such cases the flies should be screened off at some distance, as larve which have been deposited in the vicinity of meat will crawl to it, though it may not be accessible to the flies.
To prevent their attack upon wounds, the same general procedure may be adopted as recommended for the preceding species.
CALLIPHORA VOMITORIA
Blowfly.—Muscide (p. 37). Somewhat larger than house fly; eyes brownish in color; abdomen bluish green with metalic luster and usually pollinose.
The eggs are oval, white in color, and are deposited upon decomposing animal and vegetable matter and in wounds of animals. Hatching may occur in from afew hours to one or two days, the shorter periods occurring in hot weather. After from three to nine days of feeding, the matured larvee seek the ground, become buried for a short distance, and in this location enter upon their stage of pupation. The time required for the entire life cycle, including a prepupal period of several days, may be from two to five weeks, depending greatly upon temperature. Under ordinary conditions it would probably occupy about three weeks.
The blowfly agrees with the flesh fly in its habits, with the exception
DIPTEROUS LARVA: 53
that it deposits eggs instead of living larve. After hatching the manner of attack and the effect upon infested meat and wounds is much the same and calls for the same treatment.
Famity VI. CGistripa
Diptera (p. 23). Botflies, warble flies. The head is large, bearing two faceted eyes widely separated, antenne short and sunken into pits in the front of the head. The mouth parts are rudimentary, most all of the flies living in the adult stage without food. The body is heavy and somewhat hairy. The coloration is usually inconspicuous.
The larve are thick and twelve-segmented, the first two segments not always distinctly separated. There is no demarcation into body regions, only a cephalic and anal end can be distinguished. The body- segments are frequently provided with rows of spines. Buccal hooks may: or may not be present. Tracheal openings are at the posterior extremity.
The larve are parasitic in the stomach and intestines, mucous mem- branes, subcutaneous connective tissue, nasal passages, and sinuses of facial bones of mammals; other parts are also invaded by their migrations. When completely developed the larve leave these locations in the host and pass to the ground where they enter the pupal stage.
The flies of the family CEstride are of world-wide distribution.
Gastrophilus intestinalis (G. equi). Cistride (p. 53). The horse botfly (Fig. 28, h). The body of the female is one-half to five-eighths of an inch in length and is very hairy. The head, thorax and abdomen are brown. The wings are transparent with dark spots, those near the center passing entirely across the wing transversely. The abdomen is rather long and tapers to a point. In the males, which are rarely seen, the abdomen is light brown or yellow, and it is not tapering. In other re- spects the males closely resemble the females.
The larve (Fig. 28, c, d and g) when full grown are about three- fourths of an inch in length. At the head extremity are two buccal hooks by which attachment is made to the gastric mucosa (Fig. 28, e). The body-segments are bordered by short spines (Fig. 28, d).
Habits.—Like other members of the @stridz, the horse botfly at maturity is extremely active, flying chiefly during the warmest and brightest days of the summer, and generally frequenting pastures in the vicinity of woods. It is the habit of the female to hover near the horse with its long, pointed abdomen bent downward and forward. The fly then darts toward the horse, deposits its egg, retreats, and again hovers until ready to repeat the operation. The eggs (Fig. 28, a and b) are yellow in color, about one-sixteenth of an inch in length, and tapering toward the attached end, the free end being provided with an operculum which is set obliquely and gives to this end somewhat of an obliquely
54 PARASITES OF THE DOMESTIC ANIMALS
cut off appearance. They are generally deposited upon the hairs of the anterior parts of the body, as upon the forelegs, breast, shoulders, and under side of the body, regions which are most readily reached by the lips of the horse. It is not uncommon, however, for eggs to be attached to the sides of the neck, lower jaw, cheeks, mane, and other parts, the larvee in such cases reaching the mouths of horses by their licking or nipping at each other.
Life History.—The eggs are deposited rapidly with their free ends down, and adhere to the hairs by a viscid substance which quickly dries
Ore
d SN
Fie. 28—Gastrophilus intestinalis: a, egg—enlarged; b, egg—natural size; c, young larva; d, young larva—much enlarged, showing spiny armature; e, oral hooks; f, body spines; g, full-grown larva—twice natural size; h, adult female (after Osborn, Bul. No. 5, Bureau of Entomology, U. 8. Dept. of Agr.).
and gives them a firm. attachment. At this time they contain larvee which have undergone a more or less advanced development. Observations upon the botflies during recent years have been some- what disturbing to conclusions formerly held and apparently necessitate a certain revision of the life histories which have generally been given for them. According to the observations of Roubaud (1917) upon Gas- trophilus intestinalis, the eggs of the fly do not open spontaneously, and the larvee may not escape from them for several weeks. The opening of the operculum and freeing of the larva probably occurs when the horse rubs an itching or irritated area with his nose or bites it with his teeth, the horse rarely licking itself. By experiments with bot larve on guinea-pigs Roubaud demonstrated that when the hatched larva is brought in contact with the buccal mucosa it at once burrows into this membrane and lies parallel to its surface. In two or three days it dis- appears, but he notes that one was seen traveling along the side of the
DIPTEROUS LARV.E 55
tongue for nine days, during which time it grew to three times its first dimensions. Before leaving the buccal mucosa the larve probably undergo a molt and then proceed to the stomach. These observations indicate that the larve of the botfly escape from the eggs when the horse bites at his skin or rubs it with his lips, and that they burrow into the buccal mucosa where they undergo a degree of development before passing to the stomach.
Within the stomach cavity the larva fixes itself to the walls by its buccal hooks. Later the head becomes deeply inserted into an alveolus which is formed under the influence of the irritation to the mucosa. In this position the larva feeds upon the tissue juices and the products of the irritation which it sets up, becoming fully grown in about ten months. The period of larval development usually terminates from May to August, more especially in June, due to the fact that the deposition of the eggs occurs most actively in the month of August. At this time the larva becomes detached from the gastric mucosa, passes to the intestines, and with the intestinal contents leaves the body of its host.
The change into the pupal stage is made either in the horse manure or after the larva has burrowed for a short distance into the ground. At the termination of pupation, which lasts from four to six weeks, the matured fly creeps out, and, after fertilization by the male, proceeds to deposit ova for another generation.
TapuLaR Review or Lire History oF GasTROPHILUS INTESTINALIS
1. Adult Fly.—(August.)
|
2. Eggs.—Attached to hairs of horse (Aug. and Sept.);
| approximately 2 weeks.
3. Young Larve.—Upon or within mucosa of horse’s
| _mouth. .
4, Larve (Bots).—Attached to wall of horse's stomach. Stages 3 and 4 approximately 10 months.
5. Pups.—Free (June) ; approximately 6 weeks.
| 6. Adult Fly.—(August.)
" Effect.—The degree of injury due to the presence of the larve of this botfly will depend upon their number and location. That the stomach may be invaded by a considerable number of bots without apparent disturbance to this organ is probably due to the fact that they most commonly attach to the esophageal portion, this region of the horse’s stomach having a less important part in the function of digestion
56 PARASITES OF THE DOMESTIC ANIMALS
than that toward the pyloris. Where they occupy the glandular right half, especially if in large numbers, they interfere with the digestive secretion and its proper contact with the gastric contents. In excep- tional cases they may be sufficiently numerous about the pyloris to form an obstruction to the passage of food material into the small intes- tine; or even the duodenum itself may be invaded. Under these latter conditions the larve bring about nutritive disturbances and may cause attacks of acute indigestion with its accompanying manifestations of pain. When we consider, however, the large number of horses essentially harboring the larvee of the horse botfly, as indicated by the widespread prevalence of the insect, we must conclude that they are comparatively inoffensive, for in most cases there is an entire absence of any apparent disturbance and, with the exception of the voiding of the bots, nothing during the life of the animal which would lead to suspicion of their presence.
Treatment.—The larve of Gastrophilus are so resistant that treat- ment having in view their destruction or expulsion has been generally unsatisfactory. Such agents as preparations of tar, benzine and turpen- tine, which are sometimes used for this purpose, add irritation to an already irritated gastric mucosa and, for this reason, in connection with their general ineffectiveness, the advisability of their use is questionable. Where the presence of the bots in sufficient numbers to cause disturbance to the health of the animal is suspected, gastric irritation may be allayed to some extent by feeding mucilaginous materials, such as flaxseed meal. Hay in such cases is best fed chopped, and a substantial nutritive diet should be looked to as compensatory to the loss of nutriment.
A treatment recommended by Peroncito and Bosso (1894) consists in the administration of carbon bisulphide to adult horses in gelatin capsules, each containing 8 to 12 grams (2 to 3 drams). After fasting for twelve to twenty hours, the horse is given one capsule; after one hour a second capsule is given, and after another hour a third. As carbon bisulphide is strongly irritant, care should be taken in the administration of the capsules that the cap does not become detached and that they do not become crushed in the mouth.
In so far as clinical observation can determine the presence of bots, or lead to the conclusion that a remedy has caused the expulsion of any considerable number of them in proportion to the infestation, this treat- ment is said to be generally satisfactory. It seems reasonable to con- clude that an agent sufficiently active to cause the expulsion of these robust larvee from their secure attachment would have a severely irritant effect upon the gastric mucosa, though this membrane of the stomach appears to have a greater tolerance for such assaults than that of other regions of the alimentary tract.
DIPTEROUS LARVZ 57
GASTROPHILUS HEMORRHOIDALIS
The red-tailed botfly—Céstride (p. 53). Somewhat smaller than G. intestinalis. Dark brown color, yellowish hairs upon the face; trans- verse black band upon thorax. The abdomen is covered with fine hairs which in the middle are dark and posteriorly orange-red. The wings are clear.
This species of horse botfly is found in common with G. intestinalis in North America and Europe.
The females attach their ova to the hairs of the horse, preferably those about the lips. The hatched larve cause an irritation which impels the horse to pass its tongue about its lips, thus carrying the parasite into the mouth. In other respects its life history is essentially the same as that of G. intestinalis. The larve differ from those of the latter in being somewhat smaller and in their dark-red color. There is also some difference in their habitat in that they attach usually to the pyloric portion of the stomach, and when fully developed pass on to the rectum where they remain for some time, assuming a green color before being voided.
Effect.—The presence of the larve of this fly in considerable num- bers in the folds of the rectal mucous membrane may cause an annoying irritation, inducing violent efforts at defecation. Such cases, however, are extremely rare, and, as a rule, little or no evidence is given by the animal of their presence.
Gastrophilus nasalis——(stride (p. 53). This species, commonly called the chin fly, is about 1 em. (3/s of an inch) in length. The body is hairy and yellowish red in color. The wings are without spots.
Law describes the larve as “furnished with a row of spines on each ring from the second to the ninth on the dorsal surface, and as far as the tenth on the ventral. There is an unarmed part in the center of the eighth and ninth rings on the dorsal surface.”
The fly deposits its eggs about the lips and nostrils. The larve attach to the mucosa of the upper part of the small intestine.
Fitch states (1918), as to New York State, that from examination of the larve it would seem that Gastrophilus nasalis is quite as frequent as G. intestinalis.
HypopermMA Lingata AND H. Bovis
The ox botflies; warble flies (Fig. 29).—Ci stride (p. 53). Hypoderma lineata is about five-eights of an inch in length. The general color is black; body more or less covered with hairs. The front, sides, and back of the head, sides of thorax, and last segment of the abdomen are covered with long yellowish white hairs.
This fly is found in all parts of the United States, but more especially
58 PARASITES OF THE DOMESTIC ANIMALS
in the southern portion as far north as Illinois, Iowa, and Nebraska. It makes its appearance in the spring or early summer and is at once attracted to cattle, depositing its eggs on the hairs, frequently upon those about the heel, a habit which gives to the fly its southwestern name ‘‘heel-fly.”’
The entire length of the egg is 1 mm. and its width 0.2mm. _ In color it is a yellowish white. The eggs are firmly attached to the hairs by means of a clasping projec-
tion which connects with the egg proper by a short pedicle (Fig. 31). Usually they are deposited upon the hairs in groups of four to six.
Hypoderma Bovis.—(s- tride (p. 53). This species is commonly referred to as the European warble fly, though it occurs also in Canada and the United States. It is, in fact, said to be more common in some parts of this country than H. lineata. Its length, ex- clusive of the ovipositor, as stated by Neumann, is 13 to 15 mm. (1% to */s of an inch), which is 1 to 2 mm. longer than H. lineata. The
Fic. 29.—Hypoderma lineata (after Osborn, from general color is black, face alse Life, Bul. No. 5, Bureau of Entomology, U.S. gray; abdomen black; head,
ept. of Agr.). ‘
thorax, and abdomen hairy. The hairs from the base to the tip of the abdomen vary in color from white or yellow to black; orange red at posterior third. The legs are black, yellow at their terminations; wings somewhat brown.
As to the differentiation of the larve of these two species, Herms writes as follows: ‘‘The life history of the two species is very similar. The larve are different enough to distinguish them readily. The fully grown larva of H. bovis is longer, 27 to 28 mm., H. lineata about 25 mm. The two species are distinguished on the basis of their spiny armature. In . lineata each segment of the larva is provided with spines except the last, the ring upon which the stigmata are located, while in H. bovis all except the last two are armored.”
Life History.—Dr. Gooper Curtice, from his researches in 1890,
DIPTEROUS LARVZ 59
concluded that the larve of Hypoderma lineata are taken into the mouths of cattle by licking the parts where the eggs are attached, the eggs under this influence hatching at once. From the mouth the larva, according to this investigator, is carried to the esophagus, the walls of which it penetrates. While lodged in the esophagus it molts, and the body be- comes quite smooth. For a period of several months thereafter it wanders through the connective tissue beneath the skin or between muscles, and ultimately reaches a point beneath the skin of the back. Here the larva again molts and the spiny processes reappear upon its Fie. 30.—Hypoderma bovis (after Os- body. It now cuts a small opening aa taiien ea ee i aes ot through the skin, and places its anal spiracle near this orifice in order to get air. In this location the larva lives upon the products of the inflammation which its presence sets up, such as bloody serous exudate and pus. It now develops rapidly and again molts, at which time the grub is fat, yellowish-white in color, and an inch or more in length. Reaching the maturity of its larval period (Fig. 32, g and i), i which lasts about ten months, it works its way out of the orifice at the summit of the tumor and drops to the ground, into which it may burrow for a short distance. Here it enters upon the pupal stage, the hardened larval skin becoming the protecting case for the pupa within. After about four to six weeks of pupation the adult fly escapes by pushing off the cap at the end of the pupal case. Dr. Seymour Hadwen, in notes on ‘The Zz Life History of Hypoderma bovis and H. linea- tum’’ based on observations made at Agassiz, eee Rag eae ood British Columbia (Journal of the American like processes—-much enlarged Veterinary Medical Association, June, 1917) (after Osborn, Bul. No. 5, summarizes as follows: oe Ue. “Hypoderma lineatum lays its eggs as early as April 15th, but the usual laying period is during the month of May. At Agassiz they have never been cap- tured later than May 30th. Hypoderma bovis (Fig. 30) begins in the early part of June and continues up to the beginning of August.
60 PARASITES OF THE DOMESTIC ANIMALS
Between the last appearances of H. lineatum and the first of H. bovis there is usually a period of ten days when the cattle are immune from attack of either species. H. bovis frightens cattle much more than H. lineatum. The eggs take about a week to hatch; the larve bore through the skin in the coarser porous parts, taking several hours in the process; at this stage they are rather less than 1 mm. long. The lesions resulting from this penetration are caused partly by bacterial invasion and partly by anaphylactic reactions; those produced by H. lineatum being more severe. For the skin lesions I have proposed the name of hypodermal rash. At this point there is a hiatus in the life history as it is not positively known how the larve reach the esophagus, where they are subsequently found, most likely in the loose connective tissues under the skin up to the region of the throat and into the esophagus where the muscles bifurcate. Passing down the esophagus they follow the sub- mucosa and are almost always found lying along the long axis of the canal. Whilst in the esophagus small edematous swellings are found surrounding the grubs, these are sterile and are anaphylactic in char- acter, the exudate contains large numbers of eosinophilic leucocytes but no pus cells. The earliest record made at Agassiz was on August 15th, when a larva 3.4 mm. was found and several slightly larger. According to Carpenter, continental observers have found them smaller than this. H. lineatum makes its appearance in the backs of cattle about Decem- ber 15th and H. bovis about a month later. The larve at this time have grown to about 1.5 cm. and are of the same size in the neural canal and under the skin which they have just reached. At this age it is difficult to separate the larvee of the two species, but Mr. F. C. Bishopp has, I believe, discovered good distinguishing marks between the species. The life histories overlap at this period making it difficult to follow the migration, but in the latter part of the season (the middle of March) the last larvee to leave the gullet are at the paunch end. They pass out under the pleura and go to the neural canal either up the crura of the diaphragm or up the posterior border of the ribs, entering the canal by the posterior foramen, from there they descend the canal under the dura mater, emerge again through the foramen and reach the back, forming the characteristic swellings commonly called warbles. The larve follow connective tissue exclusively and no larve have been dis- covered in muscular tissue. The mature larve leave the animals’ backs from the early part of the year up to the first days of July. The periods for the two species have not been fully worked out, but judging from what records we have of the pupal period and the time of year the flies are about, H. lineatum begins to emerge in February and finishes about May Ist. H. bovis begins about May Ist and ends approximately on July 1st. The average pupal period for H. bovis is 32.5 days and for H. lineatum a little less. The duration of the life of the flies is short
61
DIPTEROUS LARVAE
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62 PARASITES OF THE DOMESTIC ANIMALS
seeing that they cannot feed. This life history applies to Agassiz, British Columbia; doubtless in other countries variations will be noticed, but the period spent by the larve within the host must be of the same duration, seeing that animals’ temperatures are the same the world over.”’
Effect.—Cattle seem to be much annoyed by the attacks of these flies in depositing their eggs, and in the endeavor to escape will often enter mire holes or injure themselves in other ways. Probably the most important damage from the insect is that to hides, these being dis- counted from twenty-five to fifty per cent. according to the number of punctures by the grubs.
Treatment.—Treatment is best applied in the months of January and February when the grubs have become sufficiently developed that the small tumors in which they are lodged may be felt by running the hand along the back of the animal. The application at this time of a little kerosene or mercurial ointment to the summit of the swelling will destroy the grub. By March the tumors may be distinctly seen as prominent lumps upon the skin of the back. The orifice at the summit is now large enough to permit of the forcing out of the grub by careful pressure. Grubs thus removed should be at once destroyed to prevent the possibility of their finding favorable conditions for development into the adult fly.
(Estrus OVvIs
The sheep botfly (Fig. 33, 1 and 2).—(é#stride (p. 53). About one- half an inch in length; yellowish-gray color; slightly hairy. The abdomen is spotted with white and yellow; posterior portion covered with fine hairs. The wings are transparent.
Occurrence and Life History.—This species is of world-wide dis- tribution, and is the most important insect pest with which sheepmen have to deal. The flies make their appearance with the coming of warm weather from early June to July, like other (stridae, flying on bright and warm days and ceasing their activities about the month of October. The female, which is difficult to observe owing to its small size and rapid flight, deposits living larvee in the nostrils of the sheep. At this time the larva is creamy-white in color and about one-sixteenth of an inch in length (Fig. 33, 6). Later it becomes darker, and at maturity reaches a length of about three-quarters of an inch (Fig. 33, 4 and 5). Upon the cephalic segment there are two hooklets the points of which are curved downward and backward. With the aid of these the larva at once pro- ceeds to work its way upward through the nasal passages until it reaches the frontal sinuses where it attaches by its hooklets to the lining mem- brane. Here it feeds upon mucus and serous exudate induced by the irritation of its presence.
The larva remains in this location about ten months, at the end
DIPTEROUS LARV.E 63
of which time, having reached its larval maturity, it detaches from the mucous membrane and passes to the nasal passages from which it is expelled by the violent sneezing which it excites in its host. Having reached the ground, it quickly buries itself, contracts within its smooth dark shell, and enters upon its pupal stage (Fig. 33, 3). After from four to six weeks of pupation the mature insect emerges.
Effect.—Both sheep and goats suffer from the attacks of this fly. Sheep are especially disturbed by it, and in their efforts to avoid its attack will toss the head, thrust the nose into the ground, or dash about in frenzy. The grubs cause much irritation to the sensitive mem- brane which lines the cavities of the head both by the hooklets with: which they make their at- tachment and by the spines cov- ering the ventral region. Further- more, if numerous, and the mucus secreted is not sufficient for their nourishment, the grubs will feed upon the membrane itself. The disturbance to the host will be manifest according to the number of grubs present; if there are but Fic. 33.—(istrus ovis: 1 and 2, adult fly;
3, pupa; 4, full-grown larva, dorsal view; few, there may be no more than 5, same, ventral view; 6, young larva. 1 and a slight ecatarrhal discharge with 2 natural size, the others enlarged (after occasional sneezing. In heavy Sai ldak aig ikl mite in Neh of infestation there is a profuse muco-purulent nasal discharge with frequent sneezing and tossing of the head, the respiratory passages in some cases becoming so filled as to bring the animal to the verge of suffocation. The appetite is lost, and emaciation and weakness may progress until there is inability to rise, death in such cases soon following.
TapuLarR Revirw or Lire History or (Estrus Ovis J. Adult Fly —(June to October.)
| 2. Hatched Embryos:—Deposited in nostrils of sheep.
3. Larve.—Attached to lining membrane of sinuses of
sheep’s head. Stages 2 and 3 approximately 10% months. 4. Pupe.—Free; approximately 6 weeks.
| 5. Adult Fly
64 PARASITES OF THE DOMESTIC ANIMALS
Treatment.—The location of the grubs and the tortuous extremity of the canals leading to such regions render the application of remedies looking to their dislodgment but partly effective at best. Benzene ap- plied by lifting the head and pouring a teaspoonful into each nostril, has been recommended. As one side is treated the head should be held elevated and the nostril held shut for half a minute. The remedy is then likewise applied to the other side. In severe cases a few of the grubs may be dislodged by a feather dipped in turpentine which is passed as far as possible up the nasal passage and rotated so as to apply it to as much of the surface as can be reached. Valuable breeding animals showing severe infestation may be treated by trephining the sinuses.
Prevention.—To prevent the fly from depositing its larve the noses of the sheep may be smeared with tar. For the convenient application of this preventive remedy many flock owners use salt logs in their pas- tures. Into these logs two-inch holes are bored at intervals of about six inches in each of which a little salt is kept during the fly season. Two or three times a week tar is smeared with a brush around these holes in such manner as to smear the noses of the sheep as they en- deavor to reach the salt. The logs should be of sufficient length to enable all the sheep to get to them.
CHAPTER VII THE FLEAS
Order II. Siphonaptera.—Insecta (p. 15). Members of this order have the body compressed laterally, and the color is usually dark brown. The head is small, generally bearing a single ocellus on each side, com- pound eyes are absent. The mouth parts are suctorial but differ from those of the order Diptera in that the true haustellum is lacking, the sucking structure consisting of the ventrally grooved labrum and the two mandibles, which form a half-open tube (Fig. 36, e and f). The maxille are sharp and serve to puncture the skin. The three thoracic segments are distinct, each bearing a pair of well-developed legs, the posterior pair being especially long, powerful, and adapted for leaping, which is the principal mode of progression.
Metamorphosis is complete. The larva are long, slender, without feet, and somewhat hairy. When mature the larva spins a cocoon and enters upon a distinct pupal stage. During this stage the pupa takes the form of the adult with the appendages enveloped in a hard pupal case. At no stage in the metamorphosis are there traces of the supposed ancestral wings. It is probable, however, that the fleas have descended from winged forms, and they are usually considered as being closely related to the Diptera.
There are many species of fleas, most of them inhabiting various wild birds and mammals. It will be sufficient here to consider the following three of the family Pulicide:
1. Ctenocephalus canis, the dog flea.
2. Ctenocephalus felis, the cat flea.
3. Pulex irritans, the human flea.
The two species of Ctenocephalus can easily be distinguished from Pulex by the presence in the former of comb-like spines on the lower margin of the head and on the hinder margin of the prothorax. These spines are dark colored, stout and closely placed (Figs. 34 and 35). The dog and cat flea have long been placed together under the one species Pulex serraticeps, but a later classification recognizes a specific difference based principally upon the form of the head. In Ctenoceph- alus canis the head, when seen from the side, is rounded in front and somewhat less than twice as long as high. The head of C. felzs, seen from the side, is more acute angled in front and is long, being fully twice as long as high. The head of Pulex irritans, with its absence of spines, is
66 PARASITES OF THE DOMESTIC ANIMALS
more regularly rounded than that of the dog flea, and bears two bristles, one low, in the vicinity of the maxilla, the other below the eye.
Life History.—In their life history the fleas undergo a complete metamorphosis. The eggs are oval, 0.5 mm. in length, and in color pearly white (Fig. 36, a). They are deposited loosely and unattached among the hairs of the host, dropping off readily during the movements of the animal. The period required for the eggs to incubate may be from one to four days or longer, depending much upon temperature.
The larvae are white, elongate, apodal, and have thirteen segments, each provided with bristles (Fig. 37). They are very active and, avoiding the light in every way possible, seek such shelter as is afforded by crev-
Fic. 35.—The human flea
Fig. 34.—The dog flea, anterior (Pulex irritans), anterior por- portion of body (after Osborn, Bul. tion of body (after Osborn, No. 5, Bureau of Entomology, Bul. No. 5, Bureau of Entomol- U.S. Dept. of Agr.). ogy, U. S. Dept. of Agr.).
ices in the floor, carpets, rubbish, or bedding of kennels, such material containing fecal or other organic matter upon which they feed, being especially favorable for their development.
The length of the larval stage varies considerably under the influence of temperature. It may be from seven to thirty days, during which time there are two molts. Just before entering the pupal stage the larva spins a white silken cocoon within which the pupa (Fig. 36, c) is lodged (Fig. 36, b). Transformation to the fully developed imago— again depending upon temperature and moisture—will occupy from five to ten days. The time required for the development of the mature insect from the deposited egg is, therefore, from thirteen to forty-four days, with twenty-eight days as probably a fair average under our ordinary climatic conditions.
Habits and Relation to Disease.—Nearly all species of fleas have some one host upon which they prefer to live, but they will often live and thrive upon other animals. The human flea will infest dogs and
67
THE FLEAS
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68 PARASITES OF THE DOMESTIC ANIMALS
cats and may be found upon these animals in common with the species usually infesting them. As a pest of the household the human flea is more commonly found in Europe and the western part of the United States, while in the eastern United States houses may be rendered un- inhabitable for a time by the presence of the dog and cat flea.
Fleas are of importance as tormenting parasites of man and domestic animals, but of late have received greater attention in the field of med- icine as carriers of disease. It is known that bubonic plague, which during recent years has made its appearance on the Pacific and Gulf coasts of the United States, is transmitted by these insects. Teeniasis of the dog, due to the presence of Dipylidium cani- y num, may be conveyed to humans as well as to dogs y through the intermediation of the dog flea, while a disease of infants known as kala azar, occurring in countries bordering on the Mediterranean, is thought to be transmitted by fleas.
Usual Hosts.—Our larger domestic animals, such as horses, cattle, and sheep, are rarely attacked by fleas. Hogs are somewhat less free from them, but, if occurring in these animals, the infestation is most always light and causes little disturbance. Dogs, cats, rabbits, fowls, and pigeons are especial ob- jects of attack. Young dogs and those chained up are more likely to be infested as they live amid conditions favorable to the breeding of the insects from the laying of the eggs to their full develop- ment, which is particularly favored by litter and = Fic. 37.—Pulex irri- wooden floors. Unlike lice, fleas do not pass their #”* larva. entire cycle upon the host, nor are they limited to a particular species. The dog and cat flea will readily attack man, and in this country is more troublesome to‘him than the human flea.
Vitality— When feeding upon blood, which is the only food taken by the adults, fleas will live from several months to a year. Off a host the dog and cat flea will not survive longer than about two months, the length of life under such conditions being considerably shortened if the weather be hot and dry.
Treatment and Control.—Where habitations are infested by these insects it is of first importance as a measure of control that dogs, cats, and other domesticated animals kept about the premises receive treat- ment that will rid them of the parasites. The harboring animals may be dusted with Persian insect powder (pyrethrum), the remedy being applied liberally and driven well under the hair, preferably after the skin has been slightly moistened. This will not kill the fleas but will stupify them, in which condition they will drop off or may be combed
THE FLEAS 69
from the hairs. It is well to place the animal while undergoing this treatment upon a large sheet of paper which may later be rolled up and burned with the collected fleas. In severe cases creolin or lysol solutions in two per cent. strength may be used. Quite effectual, but more expen- sive, is the preparation consisting of Peruvian balsam, ten parts; creolin, two parts; alcohol, one hundred parts which is recommended in the treatment for lice and scab mites upon small animals. In the treatment of cats, puppies, and chicks the powder is preferable to the last men- tioned preparations.
Following treatment animals should not be permitted to re-enter their sleeping quarters until all litter has been removed and burned. | In order that this cleaning up process may be effectual every detail must be looked to. Collections of dirt and dust between floor boards must be removed, as well as every particle of bedding or rubbish that may harbor a flea brood. After this preparation the quarters should be thoroughly cleaned with hot, soapy water and, when dry, sprayed with kerosene or kerosene emulsion (formule, page 48) as an additional pre- caution. For kennels a bedding should be used which can be frequently replaced, as shavings or straw. Carpet or matting should never be used for this purpose.
Household Infestation.—In dealing with household infestation it is first necessary to exclude flea-bearing animals from the premises or destroy the adults which are producing the eggs upon these hosts. Flea larve find excellent conditions for development under tacked-down carpets or matting and in spaces between floor boards. The floor covering, whatever it may be, should be removed, beaten, and thor- oughly aired. The floors may then be swept and the dust, which con- tains many eggs and larve, collected and burned. Kerosene should then be applied with a mop in such manner that it will penetrate all cracks and crevices in the floor and beneath the baseboards. Benzene is often advised for this purpose, but, owing to the extreme danger of ignition, its use, excepting under the most careful supervision, is not to be recommended.
Following these eradicative measures the floor coverings may be re- placed, but before doing so it is well, as an additional precaution, to sprinkle the floors with pyrethrum powder. This will work into the fabric and make the carpet or matting an unfavorable harbor for any ~ larve or adults which may have escaped the eradicative measures. Where the floors are oiled and rugs used instead of carpets or matting, the problem of getting rid and keeping rid of such an infestation is much lessened.
CHAPTER VIII THE LICE
There has been much disagreement among various authors as to the systematic arrangement of the lice. The classification given here, if . faulty, will perhaps at least serve the purposes of this work until exacting systematists have better settled the matter.
Order III. Siphunculata.—Insecta (p. 15). The Sucking Lice —The lice of the order Siphunculata have the suctorial mouth parts at the anterior border of the head, the movable proboscis being formed of the upper and lower lips (Fig. 38). Within this is the sucking-tube which is projected beyond its sheath and buried in the skin when used to aspirate blood. The eyes are two simple ocelli, one on each side. The antennz are short. The thorax is usually broader but shorter than the head, with indistinct division into three segments. The legs are short and thick, the tarsi terminating in a single claw. There are no wings. The abdomen is large and generally elliptical in outline. The last abdominal segment is rounded in the male with an opening for the penis. In the female this segment is notched and has two small terminal appendages. The female is from 1.5 to 5 mm. in length, the male somewhat smaller.
Life History.—The metamorphosis is incomplete. The young, which leave the eggs by an operculum, have the shape of the adults but do not acquire the adult color and consistency until after several molts.
The eggs as they are extruded from the female are glued fast to the hairs of the host by means of a viscid secretion. In this position they are commonly referred to as nits, which, with the aid of a hand glass, will be observed to have somewhat the shape of a barrel with the at- tached end rounded and a blunt free extremity (Fig. 40, e).
Hatching occurs in from five to six days, the young in general re- sembling the adults excepting in size. They become mature in about four weeks.
The sucking lice come into one family, the Pediculide. All are per- manent parasites, the entire life cycle being spent upon the host. All are limited to a specific host, and will only accidentally inhabit a host of a different species. Therefore if the host is known, the specific identity of the parasite is readily determined.
The characteristics of the species are here given under their respective host animals. It may be said of the sucking lice in general that the head is inserted directly on the thorax, their antenne are five-segmented; the
THE LICE 71
segments of the abdomen number eight or nine, and their tarsi are terminated by a single claw.
OrpeR IV. MaLiopHaca
The Biting Lice—Insecta (p. 15). The members of the order of biting lice resemble the sucking lice in general form, but differ from them mainly in that they are much smaller and have the mouth parts adapted for biting and mastication. They may be at once distinguished by the head and mouth parts; the head is usually rounded, triangular, squared, or crescent-shaped, and is broader than the thorax (Fig. 39). Upon the under side of the head are located the mandibulate mouth pieces adapted for cutting and feeding upon epidermic scales, hairs, feathers, and other cutaneous products. The eyes are simple ocelli located back of the short antenne and are often indistinct. The thorax is generally narrow, the prothorax being distinct, the two posterior segments fused. The legs are adapted for either clasping or running; in the first case the tarsi terminate in a single claw (Philopterida), in the second the tarsi are long and terminate in two claws (Liotheide). Wings are absent. The abdomen is generally elliptical; it may be elongate, or short and broad, approaching a globular outline. Their relatively small size and hard, flattened bodies facilitate their movement among the hairs close to the body.
In their breeding habits and life history the Mallophaga agree with the preceding order.
Although the order has been variously subdivided, it will be sufficient here to place the biting lice according to their hosts in the two families Philopterida and Liotheide, the former including the biting lice of mammals and birds, the latter the lice of birds only.
Biting lice, like the suctorial, are limited to a specific host, which as a rule they do not voluntarily leave unless it is to crawl upon another host of the same species, in which case the migration is ordinarily ac- complished when the bodies of the host animals are in contact. Under conditions of severe infestation among poultry some of the parasites may pass to the roosts and nests and, by contact, even to the body of a mammailian host, but they will not survive such migrations for more than a few hours.
PepicuLosis or Domestic MamMaLs
The condition commonly known as lousiness is medically referred to as pediculosis, a term correctly applied whether the condition be due to the presence of either the sucking or the biting species. The term phthiriasis should properly be restricted to infestation with the genus Phthirius in particular.
Lousiness is usually accompanied by an unthrifty condition, not
72 PARASITES OF THE DOMESTIC ANIMALS
necessarily resulting from, but rather predisposing to the attack, the reduction in the functional activity of the skin in such condition afford- ing an inviting habitat for the parasites. Herbivorous animals which have been kept for a prolonged period upon dry feed, as during the winter months, are those most likely to be infested, lice rarely being found upon these animals after they have been turned upon more succulent food and the winter coat has been shed.
There is, in fact, little valid excuse for the presence of these parasites upon our domestic animals at any time. Infestation is usually the accompaniment of uncleanly, impoverished, and crowded conditions of stabling or yarding. Well housed, well fed, and regularly groomed animals offer no attractions to lice, and animals so cared for will not have them. Excepting in accidental and transient incidents, their pres- ence upon man or domesticated beast reflects upon man in either case.
Whether the degree of discomfort and injury to an animal due to the presence of lice upon its body is slight or serious in its consequences will depend upon the number present and the group to which they belong. The sucking lice, piercing the skin and feeding upon the blood and exudate, cause a much more intense pruritus than that occasioned by the biting lice which, in their habit of feeding upon surface epidermic products and débris, have more the nature of scavengers.
The presence of the lice, as well as their location, is indicated by the pruritus, by their eggs or nits upon the hairs, and the débris of their molts. The irritation of the itching and rubbing, together with the loss of blood if suctorial lice are numerous, results in emaciation and general unthriftiness of an animal likely to have been in poor condition before becoming infested.
While the presence of lice may be unmistakably evident, it should be made quite sure that there is not also present a form of acariasis. Lice frequently invade animals suffering from scabies, and the pruritus, with the accompanying scaly and scabby condition of the skin, may be due to scab mites, which, minute and deeply located, may be readily overlooked. The presence of these can only be determined with cer- tainty by examination of epidermic scrapings from beneath the scabs. For their detection and examination the microscope is necessary. They are, however, often difficult to discover, and the material is best sub- mitted to a laboratory for examination if such is available. More de- tailed methods of diagnosis and treatment of this condition are given elsewhere under the discussion of the scab mites.
PEDICULOSIS OF THE HorRSE
Horses, mules, and asses harbor one species of sucking louse, Hama- topinus asini, and two species of biting lice, Trichodectes equi and T. pilosus.
THE LICE
73
1. Hematopinus asini (H. macrocephalus).—Pediculidz (p. 70). Head long and narrow; antenne attached at lateral protuberances be- hind which are notches lodging the eyes. Anterior to this the head is
more narrow with borders parallel, terminating in a blunt point. The thorax is much shorter than the head and widens posteriorly. The abdomen is oval, with stigmata placed in the middle of lateral protuberances on the margins of segments. The general color is yellow, the thorax brownish. The female is 3 to 3.5 mm., the male 2.5 mm. in length (Fig. 38).
2. Trichodectes equi (T. parumpilosus). Phil- opteride (p. 71).—Head slightly longer than broad and semicircular in front of the antennz which are set well back. The abdomen is oval
— ae
Fie. 39. — Trichodectes parumpilosus (after Osborn, Bul. No. 5, Bureau of Ento- mology, U.S. Dept. of Agr.).
and bears eight trans- verse dark bands, each plas ee a Fig. 38. — Hematopinus tion of a segment and asinj (after Osborn, from extending from the Comstock, Bul. No. 5, middle line about half Sues" o! Eatomology, U- z S. Dept. of Agr.).
way to the margin. The general color of the abdomen is yellowish, the head, thorax, and legs chestnut (Fig. 39).
3. Trichodectes pilosus. Philopteridz (p. 71).—Somewhat smaller than the preced- ing species. Head broader than long, rounded in front, and slightly widened at the temples. The antennz are inserted well forward, almost on a line with the head’s anterior border, in which respect it markedly differs from T’. equz. The abdomen tapers posteriorly and has upon the middle ofthe first seven segments darkened spots, less conspicuous than the bands simi- larly located upon T. equz. The head, thorax, legs, and abdomen are hairy on both surfaces. The general color is yellow.
Pediculosis caused by suctorial lice upon the horse is usually located at the base of the mane
and forelock, and at the root of the tail. The hairs about these parts are likely to be scant, broken, or the skin entirely denuded, due to the rubbing against anything within reach. During the act of rubbing the animal has a peculiar habit of protruding the upper lip, or, if in reach of another animal, will gently bite it.
74 PARASITES OF THE DOMESTIC ANIMALS
Biting lice are less common upon horses than suctorial. They are not often found on the upper parts of the body, more frequently occupying the regions of the neck, breast, and between the fore and hind legs. They cause less pruritus than the sucking lice, though the animals will frequently rub bare places at the regions infested. Both forms may coexist upon the same animal.
PEDICULOSIS OF THE OX
Two species of suctorial lice inhabit the ox, Hematopinus eurysternus, —the short-nosed ox louse, and Linognathus vituli,—the long-nosed ox louse. Of the biting species there is but one, T'richodectes scalaris.
1. Hematopinus eurysternus. Pediculide (p. 70).—Head relatively short: and broad, rounded in front; thorax about twice as wide as long,
Fic. 40.—Hzematopinus eurysternus: a, female; b, rostrum; c, ventral surface of the last segments of male; d, same of female; e, egg; f, surface of same greatly enlarged (after Osborn, Bul. No. 5, Bureau of Entomology, U. 8. Dept. of Agr.).
widest posteriorly. The abdomen is oval and much larger than that of the sucking louse of the horse. On the lateral margin of each abdominal segment is a slightly colored tubercle. In the female two black blotches are laterally located on the terminal segment. The general color is yellowish gray. The female is 2 to 3 mm., the male 2 mm. in length (Fig. 40).
2. Linognathus vituli (Heematopinus vituli). Pediculide (p. 70).— Somewhat smaller than the preceding. The head is long and narrow and somewhat sunken in the thorax, asin a notch. The thorax is about as broad as long. The abdomen, like the head, is long and narrow, giving to the entire insect a long and slender appearance. The general color is a deep chestnut. The female is 2.5 to 3 mm., the male 2 to 2.5 mm. in length (Fig. 41).
THE LICE
75
This species is found upon calves, though it will also,—probably as
frequently,—infest adults.
3. Trichodectes scalaris. Philopteride (p. 71).—Head cone-shaped, rounded at the temples and in front, about as broad at the temples as
long. The antennx are inserted well back and are usually directed backward. The ab- domen is not so tapering as in the biting louse of the horse, and the median spots are larger, forming bands which are quite distinct. The general coloris white. It is somewhat smaller than the species infesting the horse (Fig. 42).
This is a very common and widely dis- tributed species, frequently found upon cattle
in cohabitation with the sucking lice.
Fic. 42.—Trichodectes scalaris (after Osborn, Bul. No. 5, Bureau of Entomology, U. S. Dept. of Agr.).
Pediculosis of the ox, caused by either the short or long- Fic. 41. — Hematopinus
5 = vituli: female, under surface nosed Species, of last segments of abdomen is most likely of same (after Osborn, Bul.
No. 5, Bureau of Entomol- to be found ogy, U. S. Dept. of Agr.). about the ears, base of the head, and along the dorsal line of the neck, back, and loins. The intense itching causes the animal to rub against any convenient object, and there is frequent licking of the parts which can be reached with the rough tongue. Asa result of this rubbing large patches of skin may be entirely denuded of hair, and the skin itself in severe cases may
. become pustular and scabby.
Contrary to what has been observed in the horse, biting lice probably occur more frequently upon the ox than the sucking species, therefore lousiness of cattle is usually accompanied by less
itching. As to their location the biting lice of cattle do not limit them- selves, usually spreading to all parts of the body. They may frequently be observed crawling out upon the hairs and, when one is removed and examined with a hand glass, one or more hairs will often be found in the
clutch of its claws.
76 PARASITES OF THE DOMESTIC ANIMALS
PEDICULOSIS OF THE SHEEP
This animal has one suctorial louse,—Linognathus pedalis, and one biting louse,—Trichodectes spherocephalus.
1. Linognathus pedalis (Hematopinus pedalis). Pediculide (p. 70). —Has the same general shape as the short-nosed ox louse, but is somewhat more slender. It is also much lighter in color, giving it a somewhat immature appearance (Fig. 43).
Fie. 43.—Hematopinus pedalis: a, adult female; b, ventral view of terminal seg- ments of same; c, terminal segments of male; d, egg (after Osborn, Bul. No. 5, Bu- reau of Entomology, U. 8. Dept. of Agr.).
This species is rare. It is said to occur only where the hair is short upon the legs and feet, especially about the dew-claws. It is from this location that it gets its common name, ‘‘sheep-foot-louse.”’
2. Trichodectes spherocephalus. Philopteride (p. ‘71).—Head broad as long, giving the rounded appearance from which the specific name is derived. The abdomen is elliptical, each segment having a median band which is somewhat rounded upon its anterior border. The general color is white (Fig. 44). Of rather rare occurrence.
The common so-called “louse” of sheep is not a true louse, but the degenerate fly Melophagus ovinus, described elsewhere under the par-
THE LICE 77
asites of the order Diptera. Pediculosis, properly so called, is seldom met with in sheep. While the sucking lice are localized to the lower parts of the legs, the biting lice lie deep in the wool, close to the body, seriously altering the fleece by cutting the fibers with their mandibles. Their location makes the condition rather a difficult one to contend with.
PEDICULOSIS OF THE GOAT
Goats have one suctorial species,—Linognathus stenop- sts. The biting louse,—Trichodectes climaz, is fairly com - mon and is the only species of this genus upon goats that is well established. 4 : a
1. Linognathus stenopsis (Hematopinus stenopsis). ee aie Pediculide (p. 70).—Head long, narrow, and rounded in rocephalus (af- front; there are two lateral notches, below which are bd Oboe Pals
: ‘ o. 5, Bureau widened temples. From these the head narrows rapidly of Entomology, and becomes deeply fitted into the thorax. The thorax U. 8S. Dept. of is widest posteriorly where it is somewhat concaved upon Berl: the abdomen. The abdomen in outline is an elongated oval with stig- mata near lateral margins of segments. The female is 2 mm.; the male 1.5 mm. in length. ES
2. Trichodectes climax. Philopteride (p. 71).—Head quadrangular in shape and broader than long. The abdomen is oval with median dark bands upon the segments. The head and thorax are reddish brown; the abdomen is pale yellow.
During the winter months especially, goats are apt to harbor lice in rather large numbers. As in other animals the sucking louse produces the greater irritation. The skin may become bare in places with numer- ous inflamed and ulcerated areas covered with crusts. In Angora goats especially, the biting louse causes a great depreciation from its habit of cutting the hairs with its mandibles.
PEDICULOSIS OF THE Hog
Domesticated and wild hogs have one species of louse, Hematopinus suis (H. urius). This is the largest known member of the suctorial group. The head is very long and narrow, cone-shaped, and rounded in front; just posterior to the attachments of the antenne are horn-like protuberances, forming deep notches. The thorax is somewhat broader than long; dark, transverse bands may be noted upon the legs. The abdomen is oval in outline, with distinct segment borders; the stigmata are upon prominent lateral protuberances. The thorax is brownish red in color; the head and abdomen yellowish gray. The female is 5 mm.; the male 4 mm. in length (Fig. 45).
This louse is a very active blood sucker, living upon hogs of any age
78
PARASITES OF THE DOMESTIC ANIMALS
or condition and everywhere where these animals are found. The intensity of the pruritus produced is proportionate to the parasite’s size, the skin, as they increase in numbers, becoming covered with
papules and scales.
The constant itching and worry, which seems to
be most severe at night, is evidenced by the restlessness of the animals and their violent scratching against any available object. Such a con- dition seriously interferes with the growth and fattening of hogs, and young pigs especially will often succumb to loss of blood and ex- tensive irritation and excoriation of the skin.
PEDICULOSIS OF THE DoG
Dogs have one sucking louse, Linognathus piliferus and one biting
topinus
as long, rounded in front. The thorax anteri- orly is but slightly wider than the head; abdomen elongate oval in outline, the margins of the segments appearing somewhat rounded; stigmata marginal and distinct. The general color is yellowish white. The female is 2mm.; the male 1.5 mm. in length (Fig. 46).
2. Trichodectes latus. Philopteride (p. 71).— Entire insect broad and short; more than half as broad as long. The head large, slightly rounded in front, and broader than long. The abdomen of the female is broad and somewhat globular in outline. The median abdominal bands or spots are absent. The general color is bright yellow (Fig. 47).
Dogs do not seem to be as seriously affected as other animals by the presence of lice. The sucking louse is the more tormenting, and is usually found
Fie. 45.— Hematopinus suis (from photograph of mounted specimen, by Hoedt).
about the chin, under part of the neck, and breast,
louse, T'richodectes latus.
1. Linognathus piliferus (Hema- piliferus). (p. 70).—Head thick, about as wide
Pediculidz
Fic. 46.—Hemato- pinus piliferus (after Osborn, Bul. No. 5, Bureau of Entomol- ogy, U. S. Dept. of Agr.).
though, with the
biting louse, it may be found on any part of the body. The biting
species is most often found upon puppies.
The biting louse infesting dogs is particularly of medical interest in
THE LICE 79
being a larval host of the common tapeworm of the dog, Dipylidium caninum, as is also the dog flea, Ctenocephalus canis. Infection of the louse by the larva (Cysticercus trichodectes) is readily brought about through ingestion of the eggs of the tapeworm which may have col- lected about the anus or in the litter of the kennel. This tapeworm is occasionally found to be present in the intestines of human beings, particularly children. It is quite conceivable how such infestation might occur in the fondling of lousy or flea-infested dogs, especially if the person’s food be about at the same time to act as a vehicle for the insects containing the larva.
PEDICULOSIS OF THE CaT
Trichodectes subrostratus, the only louse harbored Fic. 47.— Tri-
by the cat, is about the same length as the biting louse chodectes _latus : (after Osborn, from
of the dog (1 to 1.3 mm.), but is not so penny, Bul. No. 5, broad, and is distinguished by its pointed Bureau of Ento- head, which is slightly longer than broad. per bcp The abdomen is oval, with median bands. iid The head and thorax are bright yellow in color, the abdo- men whitish (Fig. 48).
Lousiness is not often met with in the cat; when it does occur it is usually the accompaniment to a debilitated condition in young animals.
Fic. 48.— PEpICULOSIS OF Man
Trichodect : ae subrostratus ree species of pediculi infest man, Pediculus humanus
(after Os- (P. capitis), the head louse, P. corporis (P. vestimenti), the
a 2 an body louse, and Phthirius pubis (P. inguinalis) the pubic reau of En- OF so-called “crab-louse.”’
tomology, 1. Pediculus humanis. Pediculide (p. 70).—The head u a is somewhat diamond-shaped, short, and about as broad
as long. The abdomen has seven distinct segments, each bearing stigmata laterally placed. Color gray with darkened margins. The color is said to vary from light to dark according to the color of the skin or hair of the host. The female is 2.5 to 3 mm.; the male about 2mm. in length.
2. Pediculus corporis. Pediculide (p. 70).—Resembles preceding species, of which it is regarded by some authorities as merely a variety. It is slightly larger. The color is grayish-white. It lives upon the clothing of its host, crawling upon the body to feed.
3. Phthirius pubis. Pediculide (p. 70).—Distinctly differs in ap- pearance from the two preceding. The head is short and thick, fitting
80 PARASITES OF THE DOMESTIC ANIMALS
into a broad concavity in the thorax. The thorax is broad and appar- ently fused with the abdomen, the two forming a somewhat heart- shaped body with base anterior. The first pair of legs is much more slender than the second and third which are stout and terminated by powerful claws fitted for clasping the hairs. The female measures about 1.5 mm.; the male about 1 mm. in length. It infests the hairs of the pubic region and of the armpits, rarely passing to other parts.
Of these three species Pediculus humanus is the most widely dis- tributed.
PEDICULOSIS, CONTROL AND TREATMENT
Contagion in pediculosis is due to the rapid succession of generations of lice, their passage from host to host being facilitated by close associa- tion, grooming utensils, blankets, harness, bedding, etc. It is possible for domestic animals of different species to infect each other. Such migrations, however, are usually of an accidental nature, and the parasites will not as a rule remain to multiply upon a host foreign to them.
Long hair, especially if combined with unclean conditions, predis- poses to lousiness. If in addition there is debility, the etiologic factors become ideal. Plenty of nutritive food and a thorough cleaning up of animals and their surroundings are, therefore, essential to success, what- ever measures of eradication may be applied.
After the removal and burning of litter the stables, kennels, etc., may be treated with boiling water and afterward whitewashed or washed with a three to five per cent. creolin solution. For spraying interiors an emulsion of kerosene (formule, page 48), or the lime-sulphur prepara- tion (page 125) may be used.
Clipping of long-haired animals, which may include the horse and ox, greatly simplifies their treatment. The Melophagus infesting sheep is removed with the fleece at time of shearing, the animal soon ridding itself of any which may have remained upon the skin.
Among the considerable number of insecticide agents used upon the bodies of infested animals but one or two of those most effectual and most commonly employed need be mentioned here. A decoction of tobacco, one ounce to the quart of water, as a local application answers well for all animals. In using this preparation the possibility of nicotine poisoning should be kept in mind. Large areas of the body should not be dressed at the same time.
Horses may be treated with creolin two to three per cent., or kerosene emulsion. Brushes and combs, after having been disinfected by scald- ing, may have a little kerosene sprinkled upon them as they are used. Preparations of kerosene should not be applied to sweating animals or while they are exposed to hot sunshine. Friction with fatty substances,
THE LICE 81
as linseed oil, will kill by asphyxia lice with which it comes in contact. This treatment is more effectual if kerosene be shaken up with the oil in the proportion of one of the former to two of the latter. A mixture of kerosene, sulphur, and lard, equal parts, is also quite useful for this pur- pose.
These treatments will apply to cattle as well as to horses. Where large numbers of cattle are affected resort must be had to spraying with kerosene emulsion or dipping. For the latter purpose ordinary sheep dip or a lime-and-sulphur preparation may be used.
The large sucking louse of the hog is found principally inside, behind, and in front of the ears, on the breast, and on the inner side of the el- bows. For this animal the stronger preparations of the insecticides should be used, as creolin five per cent. or kerosene and oil equal parts. The kerosene, sulphur, and lard mixture is quite a suitable one for these animals. It is well also to treat their wallows with a three to five per cent. solution of creolin.
For dogs creolin in two per cent. strength is quite satisfactory. Long- haired dogs, especially if heavily infested, should be clipped before treatment. For small house animals, as toy dogs and cats, pyrethrum powder, applied to the moistened skin as for fleas, is most suitable.
Whatever insecticide is used it is well to apply vinegar in conjunction with it. This may be added to the fluid preparations in the proportion of about ten ounces to the quart, or it may be applied separately diluted with twice its quantity of water. The vinegar has a destructive action upon the eggs which may survive the ordinary remedies used to destroy the insects.
Sodium fluoride, which is recommended in the treatment of lice of poultry, all of which are biting lice, should also be effective for the biting lice of mammals, though experience with it up to the present time is not sufficient to have established its value in such cases. In its application it should be rubbed into the hair over all parts of the body. The treat- ment is only applicable to biting lice.
All measures used for the eradication of lice, whether in the quarters or upon the bodies of their hosts, should be repeated at least three times at intervals of eight to ten days. This is necessary to destroy the lice which may emerge from remaining eggs.
CHAPTER IX LICE OF POULTRY. THE BEDBUG
Birds under the usual conditions of domestication are especially prone to lousiness; there are, in fact, few fowls entirely free from them. Though, relative to their numbers, lice upon poultry probably do less harm than the blood-sucking ticks, their rapid multiplication, and the fact that they pass their entire cycle upon the bodies of their hosts, make it probable that any degree of infestation will become a destruc- tive nuisance. The constant annoyance due to their crawling upon the skin and among the feathers, with the energy expended in the efforts to be rid of them, causes fowl to droop and become ready victims to other diseases commonly affecting poultry. Flesh and egg production, under such conditions, must essentially be retarded to a degree commensurate to the infestation.
Young chicks are especially apt to succumb. They give evidence of the presence of lice by drowsiness, refusal to eat, and an emaciated body. The symptoms are generally accompanied by a loss of feathers, especially about the head and lower part of the neck. Chickens hatched in an incubator should be free from them, and they will remain so unless placed with a lousy hen or put in infested quarters.
The head and upper part of the neck afford a protective location for the lice, as they cannot here be reached by the beak. They may, how- ever, especially in older birds, be found upon all parts of the body.
The biting species with which birds are infested belong with either the Philopteride or Liotheide, the former containing species harbored by both mammals and birds, the latter lice of birds only.
Lick oF CHICKENS
The Philopteride of chickens are Goniocotes galline, G. gigas, Lipeurus caponis, and L. heterographus.
1. Goniocotes galline (G. hologaster)—Head broad as long; anterior border rounded; angular at temples. Abdomen sac-like in outline, hav- ing curved bands upon lateral borders of segments; transverse patches in double row. General color dirty yellow. Female about 1 mm. in length.
A common species.
2. Goniocotes gigas (G. abdominalis)—Head rounded, circular in front. Thorax narrow. Abdomen large and but slightly longer than
LICE OF POULTRY. THE BEDBUG 83
broad; each segment marked laterally by long tongue-shaped spots. The general color is yellowish. The female is 3 to 3.5 mm. in length, a size exceptional in this genus (Fig. 49).
About as common as the preceding species.
3. Lnpeurus caponis (L. variabilis).—In all members of this genus the body is elongated and narrow. Head longer than broad and rounded in front. Abdomen long and slender with black margins. Color yellowish white. Female about 2 mm. in length (Fig. 50).
_ By its long and slender appearance this species can easily be dis- tinguished from others infesting the chicken. It is not very common.
4, Iipeurus heterographus—Head more narrow in front and body much stouter than in preceding species. Abdomen elongated oval_in
Fig. 51.—Menopon pallidum (after Os- born, from Denny,
Fig. 49.—Gonio- cotes abdominalis (after Osborn, from Osborn, from
. Fic. 50.—Lipeu- rus variabilis (after
Denny, Bul. No. 5, Bureau of Entomol- ogy, U. S. Dept. of Agr.).
Denny, Bul. No. 5, Bureau of Entomol- ogy, U. 8. Dept. of Agr.).
Bul. No. 5, Bureau of Entomology, U. S. Dept. of Agr.).
outline with median spots on each ring. General color pale yellow. Female 2 mm. in length.
This species has not been often observed in this country. It is said to also occur upon certain. species of pheasants.
Of the Liotheidx chickens are hosts to two species, Menopum trig- onocephalum and M. biseriatum.
5. Menopum trigonocephalum (M. pallidum; Menopon pallidum).— Head somewhat triangular, rounded in front and at the temples. Abdo- men of female elongated oval in outline, in male longer and narrower. Legs stout and hairy. Color light yellow. Female about 1.5 mm. in length (Fig. 51).
This is the most prevalent of all of the hen lice. It is an active runner and passes readily to other species of birds.
6. Menopum biseriatum (Menopon biseriatum).—Head somewhat crescent-shaped. Legs stout. Abdomen elongate. Has the same gen-
84 PARASITES OF THE DOMESTIC ANIMALS
eral color as M. trigonocephalum, but is larger. Female about 2.5 mm. in