Identification of three members of the Anopheles funestus (Diptera: Culicidae) group and their role in malaria transmission in two ecological zones in Nigeria.

The role of the Anopheles funestus group in malaria transmission was investigated in two ecological zones in Nigeria. Sampling was carried out at four sites each around Ibadan (forest) and Ilorin (savanna). Human landing catches were supplemented with indoor and outdoor resting collections. PCR was used to identify 1848 A. funestus group mosquitoes to species level (749 in the savanna, 1099 in the forest) and three species were identified. In the forest, A. funestus s.s. predominated (55.4%), followed by A. rivulorum (27.6%) and A. leesoni (17.0%). Anopheles funestus was found mostly indoors. Anopheles rivulorum and A. leesoni predominated in outdoor collections (P<0.001). Only Anopheles funestus s.s. was found in the savanna. ELISA analysis of 803 blood meal-positive specimens showed that over half of the blood meals were taken from humans in both ecotypes. The human blood index in A. funestus from the two study areas was similar. Anopheles funestus s.s. was the only species found positive for Plasmodium falciparum using ELISA, with overall infection rates of 2.3% and 1.0% in the forest and savanna respectively. The presence of three A. funestus species in Nigeria emphasizes the desirability of correct species identification within a malaria vector control programme.