4o6 



SPECIFIC MICRO-ORGANISMS 



Diagnosis may be made by microscopic examination of the 

 blood when the parasites are numerous. At other times it is well 

 to inject s to lo c.c of blood into a white rat. The distinction 

 of Tr. brucei from other species of trypanosomes causing similar 

 diseases is not easy and may require prolonged study. 



Immunity of susceptible animals has not yet been achieved, 

 but inoculation with attenuated cultures produces a relative 

 immunity in small laboratory animals.^ 



Trypanosoma Evansi.- — This organism was discovered- by 

 Griffith Evans in 1880 in the blood of horses and various other 



Fig. 164. — Trypanosoma equiperdum. Blood of an inoculated rat. A, after four 

 days; B, after eight days. (After Doflein.) 



animals suffering from the disease known in India as Surra. - The 

 trypanosome resembles Tr. brucei in most respects but is recog- 

 nized as a distinct species. Surra is apparently transmitted by 

 various flies, TabanidcB, Stomoxys, and also by fleas. 



Trypanosoma equiperdum was found by Rouget in 1896 in 

 the blood of horses suffering from dourine. The infection is 

 tmnsmitted by coitus and probably also in other ways. Dourine 

 occurs in southern Europe and northern Africa. A few cases 

 have been observed in Canada and in the United States. Small 

 laboratory animals are susceptible to inoculation. 



1 Novy, Perkins and Chambers: Journ. Inf. Dis., 1912, Vol. XI, pp. 411-426. 



