680 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



TRYPANOSOMIASES OF ANIMALS. 



Several diseases, of great economic importance, which affect domestic 

 animals, are caused by trypanosomes; the most important of them are 

 mentioned. Tsetse-fly disease, or nagana, of Southern Africa, is caused 

 by Trypanosoma brucei and it is transmitted by Glossina morsitans; it 

 affects all domestic animals. 



In South America, mal de caderas, a disease of horses, is caused by 

 Trypanosoma equinum; it is probably transmitted by the bites of a biting 

 fly, Stomoxys. 



All through Asia, surra, caused by Trypanosoma evansi, is a severe 

 disease of cattle and equines; it is probably transmitted by the bites of 

 horse flies, Tabanidce. 



Trypanosoma dimorphon and many other trypanosomes, more or less 

 closely allied to it, cause diseases of horses, cattle, and other domestic 

 animals in many parts of Africa; they are probably all transmitted by the 

 bites of flies. 



One of the commonest trypanosomes is Trypanosoma lewisi. It is 

 usually a harmless parasite and it is found in rats in all parts of the world. 

 It is transmitted by the bites of the rats' fleas and lice. 



Dourine, oimaladiedecoit, is a serious disease of equines; it is caused 

 by Trypanosoma equiperdum. This disease was brought to North America 

 by an imported Percheron stallion. It is now endemic in some of the 

 western states and in part of southern Alberta, in Canada. It is trans- 

 mitted by coitus and, perhaps, rarely by the bites of fleas. 



A very large trypanosome, Trypanosoma theileri, occurs in cattle in 

 southern Europe and in Africa; a large trypanosome, Trypanosoma 

 americanum, resembling this one, has been found in cattle in the United 

 States; these trypanosomes seem to do no harm to their hosts. 



Although there are slight differences, the symptoms are much the same 

 in all the trypanosomiases of animals, and they much resemble those 

 which occur in the diseases produced in men by trypanosomes. Occa- 

 sionally, as in nagana, an animal trypanosomiasis may run an acute 

 course, and kill the host in two or three weeks; usually, they are diseases 

 of long duration, characterized by irregular fever, cedemas and progres- 

 sive loss of strength, weight, and energy. Localized areas of oedema 

 beneath the skin and about the genitals are especially seen in dourine; 



