Entomological patterns in the human African trypanosomiasis focus of Komo Mondah, Gabon

TL Kohagne, M M’eyi, R Mimpfoundi, J Louis

Abstract

Background: The incidence of sleeping sickness is still considerable in the Komo Mondah focus, in spite of case-detection strategy. A combined strategy that associated both mass screening and vector control is effective for the control of the disease. In the perspective of a targeted vector control in main transmission sites, we have carried out an entomological survey in the epicentre of the focus.

Objectives: To determine tsetse flies distribution, human-fly contact point and eventually risk factors for acquisition of the disease.

Methods: “Vavoua” traps were set for Glossina in four biotopes selected after an interview of HAT patients concerning their working places. Tsetse were captured and dissected. DNA from organs was analysed by PCR for trypanosome infections. The origin of blood meals was determined by ELISA.

Results: The focus is infested by three species of Glossina: G. palpalis palpalis (1149: 91.85%) found in all biotopes; G. fuscipes fuscipes (85: 6.79%) and G. caliginea (17: 1.36%) found in water spots and landing stages. They are infected by three subgenera of trypanosomes and only G. palpalis palpalis is infected by human trypanosomes. G. fuscipes fuscipes is infected by T. brucei sl and G. caliginea is not infected.  Flies are absent at the periphery of houses except in one village. Only 29.20% of blood meals were from humans. Landing stages built in swamp mangrove are presenting the higher index of epidemiological risk and populations are exposed to the disease when they go to the area for taking their fishing boats.

Conclusion: Swamp mangrove would be targeted in priority during a vector control campaign.

Key-words: Transmission, Human African Trypanosomiasis, Glossina, Gabon.