SLEEPIXG SICKNESS. 329 



studying Sleapiug Sickness will find some prophylactic or remedial 

 meisLire less obnoxious than the wholesale destruction of the 

 great game animals of Africa. 



Mr. Guy A. K. MARSHALL, F.Z.S., urged that the essential 

 question for consideration was whether or no the game consti- 

 tuted a reservoir of TrypcDWSoma rlwlesiense, as opposed to 

 T. hrucei ; and from this point of view it was somewhat unfor- 

 tunate that in giving his percentages of infected game Dr. Yorke 

 had lumped these two forms together, as this might possibly lead 

 to misconceptions. He felt very strongly that the unqualified 

 statement that human trypanosomiasis had " spread " to south 

 of the Zambesi was not justified in the present state of our 

 knowledge, and might well cause unnecessary alarm. He agreed 

 with Mr. Austen that there was no evidence to show that the 

 disease was i-eally spreading in the countries north of the river, 

 though its existence there had now been known for nearly five 

 years. A few years ago, when sporadic cases of Sleeping Sickness 

 were first discovered in JSTigeria, the fear was expressed that an 

 epidemic similar to that in Uganda would take place. Yet no 

 epidemic had occurred, nor was such an event probable ; for it 

 was now generally recognised that the disease is there endemic, 

 the bulk of the population being therefore immune, and these 

 sporadic cases merely indicated that more or less susceptible 

 individuals are still being born. The incidence of human try- 

 panosomiasis in ISTyasaland and Rhodesia presents a very striking 

 similarity with that which we find in West Africa, and, in 

 conjunction with other considerations, strongly suggests that we 

 are dealing, not with a new disease, but with one which has 

 already been endemic for some time and has merely escaped 

 detection, as in West Africa. If this be a sound conclusion, we 

 must recognise the probability that the immune natives may 

 themselves be reservoirs of the trypanosome, in which case 

 Dr. Yorke's assumption that the removal of the game must 

 necessarily eradicate the disease may prove entirely fallacious. 

 Finally, Mr. Marshall pointed out that Dr. Yorke had recorded that 

 1 in 500 of the wild flies was infected with T. rkodesiense, and had 

 referred to this as an unusually high percentage. But the latter 

 statement seemed hardly in accord with the results obtained by 

 other workers, and notably the data for T. cazalboni and T. gam- 

 biense given by Roubaud in a recent paper. Indeed, considering 

 the high percentage of infected game in the Luangwa Yalley, as 

 estimated by Dr. Yorke, his record of infected flies seemed quite re- 

 markably low and did not suggest any probability of an epidemic. 



In considering any measures for coping with human trypano- 

 somiasis in Rhodesia and Nyasaland, it is a matter of the very 

 highest importance, especially from an administrative point of 

 view, that we should ascertain whether the disease is really a new 

 one in those countries, or whether it is merely endemic. The 



Proc. Zool. Soc— 1913, No. XXII. 22 



