566 FAMILY: TRYPANOSOMID^ 



As far as present information goes, it appears that the trypanosomes are 

 transmitted by biting flies in a purely mechanical manner, but it is possible 

 that a definite developmental cycle will be discovered. Should the method 

 of transmission prove to be purely mechanical, then a new group would 

 have to be formed to include them. 



Trypanosoma evansi (Steel, 1885). — Synonyms: Spirochceta evansi Steel, 1885 

 Trichomonas evansi (Crookshank, 1886); Herpetomonas evansi (Crooksliank, 1886) 

 Trypanosoma evansi var. mborii Laverau, 1903; T. herherum Ed. and Et. Sergeut 

 1904; Trypanozoon evansi (Liihe, 1906); Trypanosoma soiidanense Laveran, 1907 

 T. hippicum Darling, 1910; T. venezuelense Mesnil, 1910; T. annamense Laveran 

 1911; T. marocanum Sergent, Lheritier and Belleval, 1915; Castellanella evansi 

 (Chalmers, 1918); T. equinum Voges, 1911 ("?). 



Under the name of surra, a disease of horses had been known for many 

 years in India. Evans (1880) described an organism he found in the 

 blood of horses, camels, and mules suffering from this disease. It was 

 rediscovered by Steel (1885), who regarded it as a spirocheete, but the work 

 of Crookshank (1886) and others revealed its true nature. The disease 

 as it occurs in India was the subject of lengthy reports by Lingard (1893). 

 Surra is now known to be caused by T. evansi, which is found naturally 

 in horses, mules, donkeys, cattle, camels, elephants, and dogs. It is, 

 furthermore, inocalable into most of the laboratory animals. 



Distribution. — Owing to the movement of horses about the world, 

 surra is now a widespread disease. It occurs in India, Burma, Assam, 

 Ceylon, South China, Siam, Sumatra, Java, Philippines, Mauritius, 

 Madagascar. Animals afterwards found to be infected have been imported 

 to Australia and the United States, but precautionary measures have 

 prevented any extension of the disease. From India it extends into 

 Persia, South Russia, Mesopotamia, and Arabia. 



Susceptibility of Animals. — The disease in horses is nearly always 

 fatal in a period varying from a week to six months. The infected 

 animals show fever, loss of appetite, anaemia, wasting, and various oedemas. 

 Similar symptoms are to be noted in camels, in which, however, the duration 

 may extend to three years, while spontaneous recovery may take place. 

 As a rule, the disease in cattle is of a milder type. T. evansi appears to 

 be much less virulent to cattle than to horses. The animals show few 

 symptoms as a rule, and nearly always recover naturally, but outbreaks 

 affecting cattle seriously have been described from Java by Penning 

 (1899, 1900) and Schat (1902), and in Mauritius by Edington and Coutts 

 (1907). Elephants are affected very much as camels are. An observation 

 by Cameron, recorded by Evans (1910) and Evans and Rennie (1910), 

 is of interest in this connection. Trypanosomiasis was discovered in a 

 herd of seven to nine elephants at Pyinmana in Burma. The trypanosome 



