Anopheles species of the mount Cameroon region: biting habits, feeding behaviour and entomological inoculation rates

Abstract

There is a lack of data on the Anopheles fauna, its biology and the roles played by different vector species in the transmission of malaria in the mount Cameroon region. The biting habits, feeding behaviour and entomological inoculation rates of different Anopheles species during the dry and rainy season were investigated. A total of 2165 Anopheles was collected, 805 in the rainy season and 1360 in the dry season. Five Anopheles species were identified: Anopheles gambiae s.l., An. funestus, An. hancocki, An. moucheti and An. nili. An. gambiae, An. funestus and An. hancocki, recorded during both seasons, were the main vectors of malaria in the region. An. gambiae s.s. was the only member of the An. gambiae (Giles) complex. These three species had their peak activity between 1 and 2 am. A human blood index (HBI) of 98.29% was recorded for fed Anopheles. The sporozoite rate, for all vectors together, was significantly higher in the rainy season (9.4%) than in the dry season (4.2%) with all the species infected by Plasmodium falciparum. The average inoculation rate was 0.44 infective bites per man per night, which adds up to 161 infective bites per year in this study area. Analyses of relative abundance and infection rate of malaria vectors at different sites situated along a transect of 20 km during the dry season showed high heterogeneity in biting and sporozoite rates. No malaria vector was caught at 1200 m a.s.l. The mount Cameroon region should be considered an area of high malaria transmission intensity.