Entomological Indices of Malaria Vectors Across Different Altitudes on Mambilla Plateau, Taraba, Nigeria

Malaria transmission dynamics and entomological indices on highlands have been a subject of interest due to their altitude. Until now, no data exist on malaria entomological indices for Mambilla Plateau; a highland region prone to malaria epidemics in Taraba, North-East Nigeria. We studied malaria entomological indices across five localities (Nguroje, Yelwa, Gembu, Kakara and Mayo Selbe) on the Plateau. Anopheles mosquitoes were collected using Pyrethrum Spray Catch method (PSC) from nineteen (19) households per locality. Anopheles mosquitoes collected were identified morphologically using standard keys. Members of Anopheles gambiae sl. were further identified molecularly. All samples were tested for Plasmodium falciparum circumsporozoite protein (CSP) using Enzyme-Linked Immunosorbent Assay (ELISA). A total of 569 Anopheles mosquitoes comprising four species; An. gambiae, An. coustani, An. funestus, and An. pharoensis were collected. Mosquito abundance and species diversity reduced with increase in altitude. An. gambiae ss. (93.92%) was the most predominant sibling species of An. gambiae complex on the highland. The presence of sporozoites was detected in 24 (4.22%) samples and all the samples were An. gambiae sl. Man biting rate of Anopheles spp. ranged between 0.02 and 2.56. Entomological inoculation rate (EIR) decreased with increase in altitude with the lowest EIR at Nguroje (0.007 bites/person/night). Results revealed that malaria transmission is ongoing on Mambilla Plateau albeit at a low rate, therefore, efforts should be geared towards malaria vector control at this time when the entomological indices suggest low malaria transmission.