THE DYNAMICS OF TRYPANOSOME INFECTIONS IN NATURAL-POPULATIONS OF TSETSE (DIPTERA, GLOSSINIDAE) STUDIED USING WING-FRAY AND OVARIAN AGING TECHNIQUES

Trypanosome infections in approximately 110,000 tsetse of 12 species o r subspecies, at sites in six African countries, were studied over var ious periods from 1983 to 1994. Infection rates ranged from 0.2% in Gl ossina fuscipes quanzensis Fires at a site in Zaire, to 18% in Glossin a tabaniformis Westwood at a site in Gabon. Statistical models were fi tted to data for nine species or sub-species of tsetse (G. pallidipes Austen, G. morsitans morsitans Westwood, G. morsitans submorsitans New stead, G. fuscipes fuscipes Newstead, G. fuscipes quanzensis Pires, G. palpalis palpalis Robineau-Desvoidy, G. palpalis gambiensis Vanderpla nk, G. tachinoides Westwood and G. tabaniformis Westwood), recorded ac ross eight sites. The prevalence of mature trypanosome infections incr eased with age, as determined by wing-fray category, for both Trypanos oma vivax- and T. congolense-type infections, although for G. palpalis , G. tabaniformis and G. tachinoides the rate of T. vivax-type infecti ons decreased in older age categories. Infection rates for T. brucei w ere very low and statistical analysis was not possible for this specie s. Overall prevalences of Trypanosoma vivax-type infections were signi ficantly higher in female than male flies in four tsetse species; G. p allidipes, G. palpalis, G. tabaniformis and G. tachinoides. At sites w here ovarian ages were also determined, close correlations between win g-fray category and ovarian age were found.