179 



THE INVESTIGATION INTO THE ORIGIN OF SLEEPING 

 SICKNESS INFECTION IN THE LUANGWA VALLEY. 



Reports have recently beeu received with reference to the search for 

 Glossbia palpalis which has been initiated by the Administration of North 

 Western Rhodesia alono- the lower half of the Luanowa River and some of 

 its western affluents, in the hopes of tracing the origin of various cases of 

 sleeping sickness which have recently been discovered in this area. But up 

 to last June no trace of palpalis had been found by either Dr. H. Leach or 

 Mr. Silverlock, after some months of independent investigation. 



Dr. Leach began his search as long ago as January last, on the Nyamadzi 

 River, which enters the Luangwa from the west near 12° S. lat. Every 

 ford and village along the river was systematically examined, but although 

 the conditions appeared generally favourable for palpalis, not a single fly 

 was found. Yet three cases of sleeping sickness were detected among the 

 resident natives. Glossina morsitans and species of Ha^matopota and Tahanus 

 were observed to be numerous along the whole course of this river. 

 The whole length of the Luangwa was then traversed in a canoe, from the 

 Nyamadzi to the Zambesi, every village near the banks being visited, and a 

 week w^as spent in examining the Kaombi and Likasashi rivers, which are 

 tributaries from the west. From Feira, Dr. Leach continued his search for 

 over 100 miles up the Zambesi to the mouth of the Kafue, and for another 

 20 miles up that river. 



Mr. Silverlock independently followed a similar course on the Zambesi, 

 but on the Luangwa his search was confined to the southern portion^ between 

 Hargreaves and Feira. Both observers note that there was a marked 

 diminution in the numbers of biting flies of all kinds as the dry season 

 progressed. 



Dr. A. May, Principal Medical Officer for North Western Rhodesia, makes 

 the following comments with regard to the present investigation : — 



'' Two portions of the Luangwa Valley are therefore under suspicion as 

 providing an agent for the spread of the disease : the northern portion in the 

 vicinity of Nawalia [on the Nyamadzi River], and the southern vicinity of 

 Hargreaves, and for some distance south. The intervening portion of the 

 river, a distance of some 200 miles, is, in Dr. Leach's opinion, unfavourable 

 for harbouring G. jjaljjalis. Between the junction of the Lusenfwa with 

 the Luangwa and the Zambesi, the conditions are also reported as unfavourable 

 for carrying palpalis. 



