Entomological survey in the historical sleeping sickness focus of Bendje (Gabon)

The situation of human African trypanosomiasis (sleeping sickness) is poorly known in Gabon. Most of the historical foci have not been investigated for more than 15 years. Few cases are passively recorded from the historical focus of Bendje; they involved mainly fishermen but determining their contamination site is difficult because of their mobility due to their activity. The presence of these cases in that focus could favour its reactivation if the vector is still there. In order to assess a potential transmission risk in that area, an entomological survey has been carried out in it. Traps were set up during four days in different habitats used by humans during their daily activities. Three species of tsetse flies (Glossina palpalis palpalis, G. pallicera newsteadi and G. caliginea) were caught and two species of trypanosomes (Trypanosoma vivax and T. brucei s.l.) were identified by PCR. These results suggest the presence of an animal transmission cycle. Human-flies contact was confirmed in all type of habitats but no transmission was quantified in the mangrove.Original Abstract: La situation de la maladie du sommeil est tres peu connue au Gabon. De nombreux foyers historiques n'ont pas ete prospectes depuis plus de 15 ans. Le foyer historique de Bendje fournit regulierement quelques cas, depistes passivement, qui concernent le plus souvent des pecheurs dont il est a priori difficile de determiner le lieu probable de contamination du fait de leur grande mobilite au cours de leurs activites. La presence des hommes infectes dans ce foyer historique pourrait favoriser son reveil s'il existe un contact etroit entre les differents elements potentiellement presents du cycle epidemiologique (homme, vecteur, trypanosome). Afin de verifier I'existence eventuelle d'un risque trypanosomien dans ce foyer, nous y avons mene une enquete entomologique. Des pieges ont ete poses dans des biotopes frequentes par I'homme et laisses en place pendant quatre jours. Trois especes de glossines (Glossina palpalis palpalis, G. pallicera newsteadi et G. caliginea) ont ete capturees et deux especes de trypanosomes (Trypanosoma vivax et T. brucei s.l.) identifiees par PCR. Ces resultats suggerent I'existence d'un cycle de transmission animal. Le contact entre les hommes et les glossines est particulierement etroit dans tous les types de site prospectes, a I'exception de la mangrove.