56 



Sleeping Sickness in Uganda. — Duration of the Infectivity of the 

 Glossina palpalis after the Removal of the Lake-shore 

 Population. 



By Colonel Sir David Bruce, C.B., r.E.S., Army Medical Service ; 

 Captains A. E. Hamerton, D.S.O., and H. E. Bateman, Koyal 

 Army Medical Corps ; and Captain F. P. Mackie, Indian Medical 

 Service. (Sleeping Sickness Commission of the Eoyal Society, 

 1908—09.) 



(Received November 16, — Read November 25, 1909.) 



During the last two years the policy of clearing the shores and islands of 

 Lake Victoria of their inhabitants has been carried out by the Uganda 

 Administration, with a view to the stamping out of Sleeping Sickness. 



It will be remembered that the area of distribution of Sleeping Sickness 

 and of the Glossina 2Mlpaiis in Uganda is the same, and is limited to a 

 narrow belt along the Lake-.shore and islands. For the past two years no 

 native has been allowed to live or work within two miles of the Lake-shore, 

 except at a few cleared landing-places; and within the last few months all 

 the islands have been emptied. 



Until recently it was l)elieved that the fly only retained its infectivity for 

 48 hours, and that it would, theoretically, be possible with safety to clear an 

 island of its infected population one day and restock it with healtliy natives 

 a few days later. Recent work, liowever, has shown this to be wrong, 

 since it has been found by experiment that the fly can retain its infectivity 

 up to 80 days. It is probable tliat after a fly has become infected it will 

 harbour the trypanosomes for the rest of its life ; but what tlie duration of 

 this is, under natural conditions, is unknown. 



From an administrative point of view, therefore, it is most important to 

 find out how long the flies on the Lake-shore remain infective after the native 

 population has been rcjmoved. Until this is known it will not be safe to 

 allow the Lake-shore and islands to be ve-inhal»itcd. 



As soon as the Sleeping Sickness Commission of the Royal Society reached 

 Uganda experiments were begun to test this point. At first the flies were 

 collected at Kihanga, a cleared landing-place in Ihika I'ay, six miles from 

 tli(i laboratory. Tliis landing-])la(!e was used as a market, where the inliabi- 

 tants of the Island of ]]uvunia came once a week to trade with the natives 

 on tlie mainland. In November, 1908, Kihanga had become somewhat over- 

 grown, and tsetse flics were prcscnl in some nunibcis. As the Duvuma 



