530 SCIENCE IN AFRICA 



of the trypanosome by tsetse, after a period of a year or fifteen 

 months. Immunity may also be acquired by sheep and goats 

 against T. gambiense. Results similar to these have followed experi- 

 ments with T. rhodesiense, which loses its power of infecting man 

 still more readily than T. gambiense, when maintained for long 

 periods in animals. Maintenance in guinea pigs is especially prone 

 to produce this change. Regarding wild animals, T. gambiense in 

 its East African form is difficult to introduce into antelopes, and 

 once introduced tends to die rapidly. T. rhodesiense, however, is 

 less susceptible; it has practically no effect on bushbuck and reed- 

 buck, but is pathogenic to oribi and situtunga; it has been shown 

 to survive in transmissible form in bushbuck for two and a half 

 years and in a hyaena for twenty- two months. The domestic fowl 

 has been eliminated as a danger in the spread of human trypano- 

 somes. 



Experiments by Dr. Duke on the prophylactic use of drugs 

 have led to the conclusion that an injection of one gram of Bayer 

 205 will protect against T. gambiense or rhodesiense for at least three 

 months. Between seventy and eighty native volunteers have been 

 used in these experiments in the past few years; there has been no 

 mishap and the results have opened up new possibilities in the 

 control of sleeping sickness (see later) . Although the trypanoso- 

 miasis institute at Entebbe no longer exists, work on kindred prob- 

 lems has continued in Uganda. In particular Dr. Mellanby has 

 been studying the bionomics of G. palpalis, with a grant from the 

 London School of Hygiene and Tropical Medicine (see Chapter 



X). _ 



From the above it appears that two important conclusions 

 have resulted from Dr. Duke's work, (i) Game animals can, 

 under certain circumstances, serve as reservoirs of human try- 

 panosomiasis, but so long as the human reservoirs can be kept 

 separate there is no need to exterminate the game. (2) Bayer 205 

 is a valuable prophylactic. For the rest, in this area, sleeping sick- 

 ness is now limited to certain foci and is certainly not of the same 

 importance as it is in the French and Belgian territories. There- 

 fore, as Dr. Duke has pointed out, work on sleeping sickness should 

 not obscure that on other diseases. 



At the Tinde laboratory in Tanganyika Dr. Corson has carried 



