Malaria vectors and urbanization in the equatorial forest region of south Cameroon

Abstract

Entomological surveys were carried out in the town of Mbalmayo and in the nearby rural village of Olama, within the equatorial forest zone of Cameroon. Mosquitoes were captured when landing on human volunteers and by pyrethrum spray catches. Malaria vectors captured were Anopheles gambiae Giles (M and S forms) and A. moucheti Evans in both areas, together with A. funestus Giles in Mbalmayo. One A. marshallii (Theobald) specimen infected by Plasmodium falciparum was found in Olama. Anopheles moucheti was the most abundant anopheline species caught in Olama, while A. gambiae was the most abundant in Mbalmayo. All these vectors were highly anthropophilic as indicated by the fact that only 5 of 201 blood meals analysed had been taken from non-human hosts. Plasmodium falciparum was the only malaria parasite species found in Mbalmayo, while P. malariae was also found in Olama. The annual entomological inoculation rate was estimated at 129 infective bites/person/year in Mbalmayo and 322 in Olama. Comparison with data published in 1955 from Mbalmayo, before expansion of the town, showed the impact of urbanization on the composition of the vector system and malaria transmission dynamics. Such changes should be considered when implementing sustainable control measures.