14 



INTRODUCTION TO PARASITOLOGY 



TABLE 1 



ANNUAL LOSSES DUE TO PARASITES OF 



LIVESTOCK IN THE U.S., 1942-1951 



(from USDA, 1954) 



♦Average annual value of animals. 



Parasites caused an estimated loss of 

 $939, 848, 000 per year. All other dis- 

 eases, both infectious and nutritional, were 

 estimated to cause a total annual loss of 

 $1,748, 594,000, so parasites are consid- 

 ered to be responsible for about 35% of the 

 losses in the American livestock industry. 

 A billion dollars a year is a sizeable fig- 

 ure. We can hardly expect to eliminate 

 this loss completely, but if every animal 

 owner took advantage of our present know- 

 ledge, a half billion dollars a year, or 

 even more, could be saved. 



Scientific Names . There are several 

 million species of animals in the world. 

 Many of them are well enough known and 

 easy enough to recognize to have received 

 common names. However, these names 

 vary from one language to another and 

 from one locality to another among people 

 who speak the same language. Further- 

 more, the same common name is often 

 applied to different species in different 

 regions. 



In the United States, "cattle" refers 

 to the ox. Box laiirus, but in India it re- 

 fers to the zebu. Bus indiciis, and in Eng- 

 land and some other countries (and in the 



Bible) to domestic livestock in general. 

 "Fowl" has more than one meaning. It 

 may refer to the chicken, Gallns domesti- 

 cus, but it may refer to any bird raised 

 for food, including the turkey, Meleagris 

 gallopavo , and ducks. Most domestic ducks 

 are Anas platyrhynchos, but the Muscovy 

 duck is Cairina moschata. One of the worst 

 offenders is "rabbit" which is applied in- 

 discriminately to many quite different spe- 

 cies. Rabbits are not rodents, but lago- 

 morphs; they have four upper incisors, 

 whereas rodents have only two. The do- 

 mestic rabbit is the common wild rabbit of 

 Europe, Oryctolagus cunicitlus. The com- 

 mon wild rabbit of North America, however, 

 is the cottontail, Sylvilagiis, of which there 

 are 13 species. In addition, there are sev- 

 eral species of jack rabbits belonging to the 

 genus Lepiis. A list of scientific names of 

 domestic and common wild animals is given 

 in Appendix I. 



In order to prevent the confusion which 

 would be inevitable in dealing with these 

 myriad species, a system of scientific 

 names has been worked out. This system 

 was first established by Linnaeus in the 

 eighteenth century, and the starting point 

 for the names of animals is the tenth edition 

 of Linnaeus' Syste»ia Naturae, which was 

 published in 1758. An International Code of 

 Zoological Nomenclature was adopted in 

 1904; it was reviewed at a colloquium held 

 in Copenhagen in 1953, and a new, revised 

 code was adopted by another colloquium 

 held in London in 1958. This code estab- 

 lishes rules for naming animal species and 

 for indicating their relationships. 



In the system of binomial nomenclature 

 used for scientific names, each species is 

 given two names. The first name, which 

 is capitalized, is used for a group of closely 

 related species; this group is called a 

 and its name is the generic name. The sec- 

 ond name, which is not capitalized, is used 

 for a single species within the genus and is 

 called the specific name. A particular gen- 

 eric name can be used for only a single 

 group of species in the animal kingdom, but 

 the same specific name can be applied to 

 species in different genera. The generic 

 and specific names are often derived from 

 Latin or Greek, but they may also be based 



