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CHAPTER X. 



TSETSE-FLIES AND BIG GAME. 



OUTBREAKS OF CATTLE TRYPANOSOMIASIS APPARENTLY DUE TO 

 BITING FLIES OTHER THAN Glossina. 



In the whole subject of Tsetse-flies, the two matters most in dispute 

 are undoubtedly the dependence or otherwise of these insects upon big 

 game for their food-supply, and its destruction as a means of combating 

 them. 



Below will be found a resume of some of the arguments put forward, 

 by the opponents as well as by the defenders of big game living in 

 regions infested by Glossina. 



There can be no doubt, as is clearly shown by Bruce, Foa and many 

 other writers, that G. morsitans has long lived at the expense of African 

 big game ; but since the latter is still very abundant in many localities 

 where the fly exists, it seems evident that these wild animals now 

 exhibit, if not complete immunity, at least a very high degree of 

 tolerance towards the trypanosomes that exist in their blood in small 

 numbers without causing serious ill effects. 1 Yet it is from this blood 

 that Tsetse-flies obtain the germs of the disease that they inoculate 

 into the blood of domestic animals. 



In the Katanga district of Belgian Congo, the simultaneous abundance 

 of big game and Tsetse in certain zones has been reported on several 

 occasions by prospectors looking for land suitable for stock-raising. 

 The more plentiful the game along the course of a stream, the greater 

 would be the numbers of G. morsitans, while tracts where there was no 

 fly would also be the poorest in game. 



Since the discovery of the transmission by G. morsitans of the 

 trypanosome known as Trypanosoma rhodesiense, which is very closely 

 related to T. gambiense and likewise produces a form of sleeping 

 sickness in man, efforts have been made to determine whether big 

 game harbours this parasite. Kinghorn and Yorke, after seeking for 

 the reservoir of T. rhodesiense in Northern Rhodesia, stated that they 

 met with the organism in the blood of the following animals : Cobus 

 ellipsiprymnus (waterbuck), Bubalis lichtensteini (Lichtenstein's harte- 

 beeste), Aepycerosmelampus (impala), Tragelaphus scriptus (bushbuck), 

 and lastly Phacochoerus ethiopicus (wart-hog) . 



Apart, however, from T. rhodesiense, which, as has just been stated, 

 is a cause of human trypanosomiasis, the same authors have shown that 

 big game may be the source of animal trypanosomiases. Out of 127 

 wild mammals, belonging to 19 genera, examined by Kinghorn and 

 Yorke at Nawalia (N. Rhodesia), 33 contained trypanosomes, the 

 following species being found to be infected : Cobus ellipsiprymnus, 



1 According to Dr. Andrew Balfour, C.B., C.M.G., who has studied the animal 

 trypanosomiases in the Lado (Upper Nile), in Southern Kordofan there is a small 

 race of black cattle, which, exactly like big game, appears to be immunised 

 to trypanosome diseases. These cattle seem to be the only ones capable of 

 continued existence in the infested Koalib zone, in which G. morsitans abounds 

 and transmits a malady which is apparently due to Trypanosoma brucei. This 

 observation may be compared with another by Dr. J. Pollard, W.A.M.S., who, 

 in his " Notes on the Tsetse-Flies of Muri Province, Northern Nigeria" (112), 

 remarks : " There is in the Munshi Division, and in the northern part of the 

 Province, a small black breed of cattle which is apparently immune to tsetse. 

 At any rate these cattle can be kept in the Munshi district where no horses 

 can live and where imported Fulani cattle all die." 



