PROTOMONADIDA 139 



individuals are produced. They develop sooner or later into 

 trypanosomes which, upon rupture of the host cell, become 

 liberated into the blood stream. This trypanosome is trans- 

 mitted by the reduviid bug, Triatoma megista and allied species. 

 The diseased condition is known as "Chagas' disease." 



B. Trypanosoma in Domestic Animals 



Trypanosoma hrucei Plimmer and Bradford (Fig. 49, c). 

 Polymorphic. Body varies from 15 to 30 microns in length 

 (average 20 microns). Transmitted by various species of tsetse 

 flies, Glossina. The trypanosome is the most virulent of all. 

 It causes the fatal disease known as "nagana" among mules, 

 donkeys, horses, camels, cattle, swine, dogs, etc., which ter- 

 minates in death of the host animal in from two weeks to a few 

 months. Wild animals are equally susceptible. The disease 

 occurs, of course, only in the region in Africa where the tsetse 

 flies live. 



Trypanosoma theileri Laveran (Fig. 49, d). Non-pathogenic 

 large trypanosome which occurs in the blood of cattle. Cosmo- 

 politan. The extremities of the body are sharply pointed; 

 length 60 to 70 microns. Myonemes are well developed. 



Trypanosoma americanum Crawley. This trypanosome was 

 noted in American cattle and is probably identical with T. 

 theileri. It is transmitted from cattle to cattle by tabanid flies. 



Trypanosoma melophagium (Flu) (Fig. 49, e). Non-patho- 

 genic trypanosome of the sheep. 50 to 60 microns long with 

 attenuated ends. The development of the organism in Melo- 

 phagus ovinus is illustrated in Fig. 48. 



Trypanosoma evansi (Steel) (Fig. 49,/). In horses, mules, 

 donkeys, cattle, dogs, camels, elephants, etc. The infection 

 in horses seems to be usually fatal and known under the name 

 of "surra." The trypanosome measures about 25 microns long 

 and is monomorphic. Transmitted by tabanid flies. Widely 

 distributed. 



Trypanosoma equinum Vages (Fig. 49, g). In horses in South 

 America, causing an acute disease known as "mal de Caderas." 

 Other domestic animals do not suffer as much as do the horses. 

 Length 20 to 25 microns. The trypanosome is peculiar in that 

 it does not show any blepharoplast by ordinary staining. 



