The Epidemiology and Control of Human Trypanosomiasis in Glossina Morsitans Fly-Belts

Abstract

The prevalence of infections with Trypanosoma gambiense has fallen by about three-quarters in the last decade, but that of T. rhodesiense has remained steady. Fly control has become very efficient against Glossina palpalis but is often disappointing against G. morsitans. This paper reviews the epidemiology of trypanosomiasis, particularly in savannah areas, and contributes original observations of the authors. The relationship of the 3 trypanosomes of the T. brucei group is considered. Study of the ecology of T. gambiense suggests that it remains confined to forest because it does produce a potent infection in animals and because of the behaviour of its vector. T. rhodesiense can infect animals and can infect G. palpalis [this Bulletin, 1961, v. 58, 1117], and there is a danger that it may invade forest belts. Food is believed to be the dominant factor in the ecology of the fly, and examples show how modifications of the wild animal population or of the vegetation may cause T. rhodesiense infection to flare up. The distribution of tsetse is determined by the tolerance of the larval and pupal stages to environmental conditions, and by the presence of suitable animal hosts for the adult. Methods of control are considered, and it is urged that this should avoid upsetting the natural resources and soil conservation principles of the area. In discussing land use the authors point out that most African soils are not rich enough for sustained agriculture. On marginal land game cropping will give a better return than cattle which are ill-adapted to the environment [ibid., 1960, v. 57, 229], Wild life conservation should be integrated in the development plans of savannah areas. The future of tsetse control lies in zoning of fly belts with sectional clearing and development of certain zones. Interesting suggestions are made for control in the immediate future and in methods of fly survey. Finally, a plea is made for a regional approach to trypanosomiasis control, and for international sponsorship of an inter-African council to integrate fly control in development plans and to secure co-ordination at both national and inter-territorial levels. The organization of research is also discussed.