74 



to the discovery of any case of disease, which is considered to be a 

 strong argument in favour of the view that the fly is here no longer 

 infective. 



Human Trypanosomiasis in G. jnorsilans areas. Since the last 

 report (Feb. 1912) 29 cases of the disease have been found — 1 European 

 and 28 natives — and the total number since August 1909 amounts to 

 95. A detailed statement is given as to the district in which the 

 various cases were found, and this shows a marked reduction as com- 

 pared with the previous survey. In the Mpika section of the Luangwa 

 area 91 per cent, of the population was palpated ; only 2 positive 

 cases of trypanosomiasis were found in 2,613 individuals, while the 

 percentages of glandular enlargement were as follows :— Men 44 per 

 cent., women 24 per cent., children 53 per cent. Similarly, in another 

 area enlarged glands were found to be very common in children (55 

 per cent.) and least so in women (37 per cent.). 



In view of the abundance of G. morsitans and the suitability of the 

 conditions, it is considered remarkable that the disease has not spread 

 in the Luangwa Valley. Dr. May offers the following possible ex- 

 planations : — (1) The disease is an old one, having in all probability 

 existed for a considerable number of years before it was recognized, 

 and is endemic, the bulk of the population being immune ; (2) the 

 extent to which game is infected with T. rhodesiense may not be so 

 extensive as has been suggested ; (3) the facts suggest that there is 

 still a link wanting in the chain of evidence in favour of the view that 

 the trypanosome of the game is identical with that which causes 

 human trypanosomiasis. 



This last criticism is further emphasised and reference is made to 

 Dr. Taute's experiments upon himself. For an experiment to inves- 

 tigate the relationship between game and Glossina and betw^een game 

 and human trypanosomiasis, the Lukasashi Valley, north of the 

 Nkuski-Petauke road, is considered to be an eminently suitable 

 locality. It is suggested that the area to be dealt with should be not 

 less than 400 square miles, that it should be effectively fenced, and that 

 the experiment should extend over three years. The cost is roughly 

 estimated at £11,350. 



One or other of the following conditions will be found to result from 

 this experiment : — (a) the total absence of fly from the area cleared 

 of game ; (6) a diminution in the amount of fly present ; (c) un- 

 changed conditions as regards the prevalence of fly. In the event 

 of either (a) or (6) being found to have followed the removal or de- 

 struction of game within a given area, it will then be necessary to 

 determine : — (1) whether the fly has died as the result of the removal 

 of one of its sources of food-supply ; or (2) whether the fly has migrated 

 in search of food. Until a method for the determination of these 

 essential points be available an experiment giving these results will be 

 open to grave doubts. If condition (c) results after the removal of 

 game, this also will not be in any sense conclusive as to the effect of 

 the experiment. Our present ignorance of the binomics of this fly, 

 and therefore our inability to interpret correctly the results following 

 such an experiment, leads to the opinion that it would not be justified 

 by its results. The present agitation for the general destruction of 

 game as a preventive of the spread of sleeping sickness does not appear 

 to the author to be well grounded. Exception is taken to various 



