ARE STABLE FLIES (DIPTERA, STOMOXYINAE) VECTORS OF TRYPANOSOMA-VIVAX IN THE CENTRAL-AFRICAN-REPUBLIC

The epidemiology of Trypanosoma vivax infections was studied at a rive rside site in the Ouro-Djafoun livestock area situated in the Central African Republic during the period between July 1991 and July 1992. Th is paper examines the possibility that stable flies (Diptera: Stomoxyi nae) were also vectors of this trypanosome species in a non-cyclic way . Previous studies have revealed that the usual cyclic transmission by the tsetse fly Glossina fuscipes fuscipes was probably not the only t ransmission route. At the study site, at least five species or subspec ies of stable flies were encountered: Stomoxys nigra nigra (approximat ely 60% of the sample), S taeniata, S sitiens, S omega omega and Haema tobia spp. The hypothesis that stable flies could be good vectors of T vivax this country is supported by three main observations: i) stable flies were very abundant at the cattle resting site; ii) an estimatio n of the 'contact index' between the cattle and stable flies demonstra ted close interactions between cattle and stable flies at this site, p articularly during the rainy season, and iii) there was a good correla tion (P < 0.05) between the apparent stable fly densities at the resti ng site and the frequency of T vivax in the cattle. The relevance of t his phenomenon in terms of epidemiology and combatting T vivax-caused nagana is discussed.