Insecticides Susceptibility of Malaria Vectors in Okitipupa, Ondo State, Nigeria Using WHO Susceptibility Test

: Pyrethroid insecticides are recommended for use in long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) due to their low mammalian toxicity and fast action. Currently pyrethroid resistance has been reported in western and eastern Africa, therefore monitoring resistance is important in all malaria endemic countries. The overall goal of this study is to monitor resistance levels in malaria vectors in Okitipupa. Susceptibility of malaria vectors to insecticides was determined in Ayeka, Idepe, Igbodigo and Okitipupa districts of Okitipupa town using WHO test. Three sentinel sites from each district were selected and mosquitoes were collected from each sentinel site. The collected Anopheles mosquitoes were reared to adults in the insectary of the Department of Biological Sciences of Olusegun AgaguUniversity of Science and Technology, Okitipupa. Two to five days old An. gambiae mosquitoes were assessed for resistance levels to Pirimiphos-methyl (0.25%), Lambdacyhalothrin (0.05%), Bendiocarb (0.1%), Permethrin (0.75%) and Propoxur (0.1%). Knockdown time (KDT) was recorded up to 60 minutes and maintained for 24hrs post-exposure on 10 % glucose solution, after which mortality was recorded. The susceptibility test showed that mosquito mortality after 24 hrs for Pirimiphos-methyl was 25%, Lambdacyhalothrin was 0%, Propoxur was 75%, Bendiocarb was 100% and Permethrin was 50%. This study revealed development of resistance to Pirimiphos-methyl, Permethrin and Lambdacyhalothrin in An. gambiae s. l. across all sentinel sites. The implication of this was discussed and suggestion for monitoring was made before this problem becomes widespread in Okitipupa town.