THE DISTRIBUTION OF THE TSETSE-FLIES GLOSSINA-MORSITANS-SUBMORSITANS AND G-PALPALIS-GAMBIENSIS (DIPTERA, GLOSSINIDAE) IN THE GAMBIA AND THE APPLICATION OF SURVEY RESULTS TO TSETSE AND TRYPANOSOMIASIS CONTROL

A country-wide survey of the distribution of tsetse flies Glossina morsitans submorsitans Newstead and G. palpalis gambiensis Vanderplank was carried out in The Gambia, during 1989-1990, using box traps at 1654 sites over an area of 10,000 km2. The general distribution of tsetse had changed little during the last 45 years. G. m. submorsitans was present in dry, canopied woodland throughout most of the country, but was absent from an area south of the River Gambia stretching from the coast to some 100 km inland. G. p. gambiensis occurred in evergreen forest and woodland near the coast, and in riparian habitats along the length of the River Gambia and its major tributaries. Nowhere in the country was more than 20 km from tsetse-infested areas. Five major foci of G. m. submorsitans infestation were identified. Demographic, climatic and environmental factors affect tsetse populations in The Gambia, but it is expected that these foci of infestation will persist for at least the next 5-10 years. The numbers of tsetse trapped, expressed as relative densities, were used to assess the extent and severity of losses from trypanosomiasis to different categories of livestock. Survey results such as these could be used to assess whether control measures to reduce tsetse challenge are likely to be economically viable by using techniques such as insecticide-impregnated targets, pour-ons or chemotherapy.