BASELINE SURVEY ON THE INSECTICIDE RESISTANCE PROFILE OF ANOPHELES GAMBIAE (DIPTERA: CULICIDAE) TO SELECTED INSECTICIDES IN IGBOKODA, SOUTHWESTERN-NIGERIA

Abstract

Malaria is a growing concern in African countries, including Nigeria. Among the multiple malaria control approaches, insecticides are of key importance, and this main practice is threatened by the emergence of resistance in malaria vectors. Studies on the susceptibility of Anopheles towards insecticides are lacking in Igobokoda Southwestern-Nigeria, and this study investigated the susceptibility status of Anopheles gambiae s.l using five selected insecticides including permethrin (0.75%), lambda cyhalothrin (0.05%), propoxur (1.0%), bendiocarb (0.1%) and pirimiphos-methyl (0.1%), which are frequently used as control against the vector population. Immature stages of Anopheles mosquitoes were collected using 350mL deep ladles and scooping spoons and bred in the laboratory following the WHO standard protocols. Mosquitoes aged between 2-5 days were exposed to the selected insecticides using the WHO standard test procedure. Knock down time (KDT) for 50 and 95% was determined using probit analysis. Mortality of mosquitoes exposed to bendiocarb was 100%, followed by propoxur (98%), pirimiphos-methyl and permethrin (95%) and least was observed for lambda-cyhalothrin (67%). Percentage knockdown was highest in bendiocarb compared to other insecticides and the difference was significant (F=5.2, P<0.0001). KDT50 and KDT95 ranged between 12.07 to 54.12min and 28.18 to 91.38min, respectively, and was lowest for bendiocarb (12.07 and 28.18min, respectively). This study therefore imperatively suggests the continuous use of permethrin, adoption of bendiocarb and combined insecticides on the treated long lasting bed nets as well as indoor coating of walls or spraying.