The dynamics of trypanosome infections in natural populations of tsetse (Diptera: Glossinidae) studied using wing-fray and ovarian ageing techniques

Abstract

AbstractTrypanosome infections in approximately 110,000 tsetse of 12 species or subspecies, at sites in six African countries, were studied over various periods from 1983 to 1994. Infection rates ranged from 0.2% inGlossina fuscipes quanzensisPires at a site in Zaire, to 18% inGlossina tabaniformisWestwood at a site in Gabon. Statistical models were fitted to data for nine species or sub-species of tsetse (G. pallidipesAusten,G. morsitans morsitansWestwood,G. morsitans submorsitansNewstead,G. fuscipes fuscipesNewstead,G. fuscipes quanzensisPires,G. palpalis palpalisRobineau-Desvoidy,G. palpalis gambiensisVanderplank,G. tachinoidesWestwood andG. tabaniformisWestwood), recorded across eight sites. The prevalence of mature trypanosome infections increased with age, as determined by wing-fray category, for bothTrypanosoma vivax- andT. congolense-typeinfections, although forG. palpalis,G. tabaniformisandG. tachinoidesthe rate ofT. vivax-type infections decreased in older age categories. Infection rates forT. bruceiwere very low and statistical analysis was not possible for this species. Overall prevalences ofTrypanosoma vivax-type infections were significantly higher in female than male flies in four tsetse species;G. pallidipes, G. palpalis, G. tabaniformisandG. tachinoides. At sites where ovarian ages were also determined, close correlations between wing-fray category and ovarian age were found.