Distributions of Glossina and Epidemiological Patterns in the African Trypanosomiases

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Ford J.
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The principal distinction between the trypanosomiasis situations of West and East Africa, or, more precisely, between those portions of the continent infested with, or lacking, tsetse flies of the palpalis group, is that where these flies are present man and his animals may become infected by a vector which ramifies throughout the human habitat and, where they are absent, man and his domestic animals become infected when they enter or approach too close to the habitat of Glossina. Clearly the reference is to populations. The women who carry their water pots to the small dry season foci of Glossina pa/palis on Northern Nigerian rivers to form what Nash (1948) has called "close personal contact" are, evidently, as individuals, entering a Glossina habitat; but they are not moving away from their normal, everyday, homes in the same way as the honey hunters of Tanzania who travel fifty miles into the bush to collect the products of their hives (Apted et aI. 1963). The distinction is clearest in the case of the cattle trypanosomiases. Mornet (1954) published maps which showed a zonation in relative frequency of diagnosis in cattle of Trypanosoma vivax and T. congolense stretching from the southern edge of the Sahara to the coast of the Bight of Benin. The important point is that the data were collected from animals pastured in or seasonally migrating throughout the whole depth, some 700 miles, of the West African tsetse-infested country. In the palpalis-free lands of eastern and southern Africa, overlapping of cattle pasture and tsetse-belts is very slight. Infection appears in a narrow band, showing, at any rate in some areas, a similar zonation of the two common cattle trypanosomes, but only five to twenty-five miles wide around the peripheries of the G. morsitans West. and G. swynnertoni Aust. fly-belts (Ford 1964).
American Journal Of Tropical Medicine And Hygiene, 68, p. 211-225