384 TRYPANOSOMA THEILERI [CH. 



2. Trypanosoma theileri Laveran, 1902. 



Synonym. T. transvaaliense Laveran. 



General account. This trypanosome was discovered by 

 Theiler in 1902, occurring in the blood of cattle in the Transvaal. 

 It was named and described by Laveran, in 1902, who at the 

 same time distinguished two species of trypanosomes occurring 

 in the blood of cattle in the Transvaal, viz. T. theileri and T. 

 transvaaliense. Theiler has shewn that the latter is merely 

 a young stage in the development of T. theileri, for when blood 

 containing transvaaliense was injected into cattle the latter 

 developed infections of typical theileri. 



The pathogenic effects of this trypanosome are so slight, 

 that no difference can be detected between normal and infected 

 cattle. 



Since the discovery of T. theileri, non-pathogenic trypano- 

 somes have been found in the blood of catt e from all parts of the 

 world. In the majority of cases the parasites are present in 

 such scanty numbers that their presence can only be detected 

 by means of culturing the blood of the infected animals, but in 

 others the trypanosomes are in sufficient quantity to be evident 

 on ordinary microscopic examination. Considering the fact that 

 cattle infected with T. theileri in Africa frequently shew very 

 many parasites in the circulating blood, whereas in the case 

 of infections with T. americanum, franki, rutherfordi, etc., the 

 trypanosomes are always excessively rare, the specific identity 

 of these forms seems a little doubtful. However, there is 

 a possibility that the numerous non-pathogenic trypanosomes^ 

 described under different names ^ from practically every 

 part of the world, only constitute one species, and therefore 

 the observations in this chapter only refer to T. theileri as 

 observed in the Transvaal. 



Morphology of the parasite. T. theileri is remarkable because 

 of its relatively enormous size. The large forms measure as 

 much as 60 to 70 microns in length by 4 to 5 microns in 

 breadth. The transvaaliense forms, which are probably stages 



^ Among these may be mentioned T. himalayanum, indicum and mukiesari 

 Lingard, 1904 ; T. franki Frosch, 1909 ; T. wrublewskii, T. americanum 

 Crawley, 1909 ; T. rutherfordi Hadwen, 1912. 



