Malaria transmission in a region of savanna-forest mosaic, Haut-Ogooué, Gabon

Abstract

During the 2 years 1993 to 1995, an entomological survey was carried out in the savanna-forest area of Franceville, Gabon, investigating malaria transmission in one suburban district of Franceville (Akou) and in one rural village (Benguia). The biting rates of the Anopheles vectors were 10 times higher in the rural zone compared to the suburban zone. Anopheles funestus Giles was the predominant species in both zones followed by Anopheles gambiae s.l. Giles. The densities of Anopheles nili Theobald and Anopheles moucheti Evans were very low. In the suburban zone, transmission was maintained throughout the year by An. funestus and An. gambiae s.l., whereas in rural zones the secondary vectors An. nili and An. moucheti were also involved in transmission. Humans in a suburban setting received one infective bite per person every 4 days, whereas in the rural area the infective biting rate was 4 times higher. Considering each vector, the observed entomological inoculation rates (EIRs) were one infective bite per person every 6 and 17 days for An. funestus and An. gambiae s.l., respectively, at Akou. At Benguia, the EIRs were one infective bite per person every 2, 3, 6, and 19 days for the 4 An. funestus, An. gambiae s.l., An. nili, and An. moucheti, respectively. The predominance of An. funestus over An. gambiae s.l. and its high EIR make it the most important malaria vector in this region of Haut-Ogooué.