Insecticide Resistance in Anopheles gambiae s.l Mosquitoes in Awka, Anambra State, Southeast Nigeria

Long-lasting insecticide nets (LLINs) and indoor residual spraying (IRS) are the main methods used for malaria vector control. However, the success of these methods has been hampered by the development and spread of insecticide resistance in major malaria vectors. The emergence of insecticide resistance in Anopheles mosquitoes in Nigeria has enormous implications for vector control interventions in the country. This study aimed to investigate the insecticide susceptibility levels of wild Anopheles gambiae mosquitoes from Southeast, Nigeria to the four main classes of insecticides used for vector control. Larval mosquitoes were collected from different breeding sites and reared in the insectary. Mosquitoes were identified morphologically and two to five day old adult female mosquitoes were used to conduct WHO susceptibility assays against pyrethroid (0.75% permethrin and 0.05% deltamethrin), organochlorine (4% DDT), organophosphate (0.25% pirimiphos-methyl) and carbamate (0.1% propoxur and 0.1% bendiocarb) insecticides. All mosquitoes collected were identified as members of the Anopheles gambiae s.l. The mosquitoes were completely susceptible to bendiocarb (100% mortality). Resistance to permethrin, pirimiphos-methyland DDT was recorded with percentage mortalities of 26.5%, 17.5% and 1.3% respectively. The KDT 50 recorded were 36.7 minutes (0.1% Bendiocarb), 39.8 minutes (0.1% propoxur), 50.9 minutes (0.05% deltamethrin), 91.4 minutes (0.75% permethrin), 116.3 minutes (0.25% Pirimiphos-Methyl) and 119.1 minutes (4% DDT). The results show that there is very high frequency of insecticide resistance in the study area and calls for a need for insecticide resistance management strategies to be implemented in the area.