TRYPANOSOMA RHODESIENSE 547 



another source of infection existed. The wikl fauna was examined, and 

 it was discovered that 24 per cent, harboured trypanosomes. In later 

 investigations in Nyasaland, Bruce et al. (1913e) found that as many as 

 31-7 per cent, of the wild game harboured T. brucei or other species 

 pathogenic for domestic animals. Similar results were obtained by 

 Kinghorn and Yorke {I9l2a) in North-East Rhodesia, but they wrote of 

 the trypanosome as T. rhodesiense, which, however, they regarded as 

 identical with T. brucei. The wild game do not appear to be seriously 

 afJected by their infections, and it is evident that they form a reservoir 

 for the virus, which is transmitted to domestic animals by the tsetse flies 

 (see p. 508). On account of the wild fauna, development of these countries 

 is handicapped to such an extent that some have advocated the complete 

 extermination of the game. If, as seems probable, T. rhodesiense is 

 identical with T. brucei, then the question is a still more important one. 



The Human Strain of Trypanosoma brucei. 



Trypanosoma rhodesiense Stephens and Fantham, 1910, — This try- 

 panosome, which produces a disease in man differing in many respects 

 from that caused by T. gambiense, was first recognized as distinct from the 

 latter by Stephens and Fantham (1910). The chief feature not shown by 

 T. gambiense is the presence of posterior nuclear forms in small laboratory 

 animals inoculated from man. The disease in man is of a more serious 

 type than that produced by T. gambiense, and runs a course of only a few 

 months. It is only exceptionally that the symptoms characteristic of 

 sleeping sickness appear. The disease is too rapidly fatal to allow of the 

 changes in the central nervous system which occur in the more chronic 

 infections with T. gambiense. 



Distribution. — The disease in man has a very restricted distribution 

 when compared with sleeping sickness due to T. ga^nbiense. It is limited 

 to the districts east and west of Lake Nyasa, and occurs in Northern 

 Rhodesia, Nyasaland, the south-east corner of Tanganyika Territory, 

 and the north-east part of Mozambique. Cases have also been recorded 

 from South Rhodesia near Livingstone. Outside this area, in w^hich 

 T. gambiense infections do not occur, there are only two records of the 

 occurrence of the infection. Duke (1923) studied an epidemic at Mwanza 

 in the district bordering the south-east corner of Victoria Nyanza, while 

 Archibald (1922) isolated from sleeping sickness cases in the Southern 

 Sudan a trypanosome which corresponded morphologically with T. brucei. 

 Though T. gambiense infections occur at the north end of Lake Victoria, 

 they have not been recorded from Mwanza, the only district where the 

 two infections appear to overlap being in the Southern Sudan. 



