Susceptibility and resistance status of malaria vector to pyrethroid and organophosphate insecticides in Ondo State, South West, Nigeria

Abstract

Malaria is a major infectious disease that still affects nearly half of the world’s population. In malaria control programs, understanding local resistance dynamics is crucial for effective vector management. Information on the susceptibility of malaria vectors in the study area is needed to improve malaria control efforts. This study investigates the susceptibility and resistance patterns of malaria vectors to pyrethroid and organophosphate insecticides in Ondo State, Nigeria. The research involved collection of mosquito larvae from six different locations conveniently selected from three senatorial districts in Ondo State, Nigeria. Mosquito larvae were collected and taken to the Laboratory insectary and reared to adults, and sorted. The results obtained indicates the female An. gambiae s. l. was the most
predominant malaria vector in the state (41%). A batch of 25 adult An. gambiae s. l per location were subjected to four insecticides for susceptibility testing using CDC WHO methods. The results show the Anopheles species were more susceptible to deltametrin 0.05%, (100%), alphacypermerin 0.05%, (95%), primiphos-methyl 0.25%, (99%), and compared to permethrin, 0.75% (73%), but the difference was not statistically significantly different p=0.12. Intensity assay conducted on mosquitoes resistant to x1 concentration of permethrin shows 100% susceptibility to x5 concentrations of permethrin except in Ipogun having 100% susceptibility with x10 concentration (p >0.005). The findings highlight a growing resistance to pyrethroids with some populations also showing reduced susceptibility to organophosphates an indication of need for continuous monitoring and to diversify vector control strategies to sustain the effectiveness of malaria efforts in the region.