Prophylaxis 555 



The period of lethargy seems to coincide with that at which the 

 parasites are invading and injuring the nervous tissue. 



Prophylaxis. — Reasoning from knowledge of the successful cam- 

 paigns that have waged against yellow fever and paludism, it at 

 first appeared as though the prophylaxis of sleeping sickness ought 

 to be based partly upon measures taken to prevent the infection 

 of men by tsetse-flies, and partly upon those taken to prevent the 

 infection of the flies by men. 



To prevent the infection of men by the flies is extremely difiicult 

 where naked or half-naked savages are to be dealt with. For 

 Europeans, the customary dress, the avoidance of exposure in bath- 

 ing, the use of mosquito guards, etc., are to be recommended, as well 

 as the erection of habitations and the building of roads, etc., as 

 far as possible from the fly districts. The destruction of the grass 

 and reeds along the river banks, the use of drainage, and the intro- 

 duction of chickens, to pick up the larvae and pupa£, have been 

 recommended. 



To prevent infection of the flies with Trypanosoma gambiense is 

 impossible where, as in some sections of Africa, 50 per cent, of the 

 population of some of the villages already harbor the parasites, 

 and still more impossible when, as is the case with Trypanosoma 

 rhodesiense, the wild animals, especially antelopes which are ex- 

 tremely numerous, continually harbor the parasites and act as 

 reservoirs from which the flies receive a continuous supply. 



The importance of undertaking radical measures for the prevention 

 of the disease may be imagined when it is understood that in the 

 last few years no less than a half -million of the natives of the infected 

 districts have died of sleeping sickness. 



Tsetse Flies 



The Tsetse flies are dipterous insects belonging to the family Glossiniae, and 

 included in a single genus Glossiua. With one exception, G. tachinoides, the 

 entire family lives in tropical and subtropical Africa. About sixteen species of 

 Glossina are now described, for the rough and ready identification of which the 

 following table from Brumpt ("Precis de Parasitologie, " 1910, p. 630) will be found 

 useful. For those who desire more accurate information, Austin's "Handbook of 

 the Tsetse Flies," the "Sleeping Sickness Bulletin," and Patton and Cragg's 

 'Text-book of Medical Entomology" wiU prove useful books of reference. 



Tsetse flies are easEy recognized by their fly-like appearance, by their hori- 

 zontal proboscis, slender but swollen at the base, and by their habit of resting with 

 the wings crossed like the blades of a closed pair of scissors. 



The greater number of the flies occupy sections of country, spoken of as "fly 

 belts" or "fly districts," some of which are permanently infected, others tem- 

 porarily infected. Such "belts" are usually deep forests along the banks of 

 streams or on the shores of lakes. The adult flies seem to love the shade, though 

 they fly from it into the hot sun to seek their prey. The large game animals seem 

 to be the natural prey of the flies, though a number of them bite human beings, 

 and one, Glossina palpalis, seems to prefer human blood to all others. The flies 

 seem to attack moving animals by preference. So long as the creature moves 

 they pursue. When it stands, many of them fly away to the shade again. 



Both males and females bite. The latter distend themselves with blood until 



