TRYPANOSOMA EVANSI 95 



suspected until comparatively recent times. It has been shown by 

 Stephens and Blacklock (1913) that the original Zululand strain of 

 T. brucei was monomorphic, while the organism sent from Uganda, 

 and at the time believed by Bruce to be the same as the Zululand 

 trypanosome, has been found to be polymorphic, with morpho- 

 logical resemblances to T.rhodesiense. Stephens and Blacklock 1 have 

 suggested the name T. ugandce for the polymorphic trypanosome, 

 which, however, has marked resemblances with Trypanosoma 

 pecaudi, and they are, perhaps, identical. T. pecaudi was the name 

 given by Laveran 2 in 1907 to the causal agent of " baleri " in equines 

 and sheep in the French Sudan. T. pecaudi, which is dimorphic, 

 is widely distributed in Africa. An extremely small number of both 

 T. pecaudi and T. ugandce have been shown to possess posterior 

 nuclei. T. pecaudi is transmitted by various species of Glossina, 

 and is said to develop in the gut and proboscis of the fly. 



On the other hand, Bruce and colleagues (1914), examining a 

 strain sent from Zululand in 1913, state that T. brucei is polymorphic. 

 Bruce (1914) suggests that passage through laboratory hosts has 

 influenced and altered the morphology of the parasite. 



Trypanosoma evansi, Steel, 1885. 



Syn. : Spirochceta evansi, Steel, 1885; Hcematomonas evansi, Crookshank, 1886; 

 Trickomonas evansi, Crookshank, 1886. 



Trypanosoma evansi, first found by Evans in 1880, in India, is the 

 causal agent of the disease known as " surra." The malady affects 

 more particularly horses, mules, camels and cattle in India and neigh- 

 bouring countries, such as Burma and Indo-China. It occurs also in 

 Java, the Philippines, Mauritius and North Africa. Elephants may 

 be affected. A serious outbreak among cattle in Mauritius occurred 

 in 1902, the disease being imported into the island. The symptoms 

 are fever, emaciation, oedema, great muscular weakness and paralysis 

 culminating in death. 



T. evansi varies from 18 //, to 34 //, in length and i'5 //. to 2 //, in 

 breadth. It has a pointed posterior extremity, and, anteriorly, there 

 is a free portion to the flagellum (fig. 41). It is possibly mono- 

 morphic, but a few broad forms occur. The trypanosome multiplies 

 by longitudinal fission in the blood. Rounded leishmaniform stages 

 occur in the spleen of the vertebrate host, which stages Walker 3 (1912) 

 considers to be phases of schizogony. 



The parasite is transmitted in nature by various species of Tabanus 

 and Stomoxys, though at present little is known of the life-history 

 within these invertebrate hosts. 



1 Proc. Roy. Soc., B, Ixxxvi, p. 187. 2 C.R. Acad. Sci., cxliv, p. 243. 



3 Philippine Journ. Sc. (Sect. B), vii, p. 53. 



