The major and minor Aedes mosquitoes from southern Nigeria exhibit low resistance towards public health insecticides

Abstract

Insecticide-based interventions continue to serve as the cornerstone of Aedes mosquito control, the primary vectors of arboviruses. This study assessed the insecticide resistance profiles of four Aedes mosquitoes in three rural areas in southern Nigeria, where arbovirus outbreaks recently occurred. Using WHO tube tests and CDC bottle bioassays, four Aedes species (Aedes aegypti, Ae. albopictus, Ae. simpsoni complex and Ae. luteocephalus) were evaluated for susceptibility to commonly used public health insecticides, including deltamethrin, alphacypermethrin, permethrin, pirimiphos-methyl, chlorfenapyr and clothianidin. Biochemical assays were conducted using Ae. albopictus to establish the role of metabolic resistance mechanism. Amplification and sequencing of fragment of Ae. luteocephalus ITS1 gene molecularly confirmed its species identity. Aedes aegypti exhibited possible resistance to pirimiphos-methyl but remained susceptible to all other insecticides across study sites. Aedes albopictus showed resistance to DDT and possible resistance to pirimiphos-methyl, while remaining susceptible to pyrethroids. Aedes luteocephalus was resistant to pirimiphos-methyl but susceptible to all other insecticides. Aedes simpsoni complex was fully susceptible to all insecticides. Biochemical assays revealed elevated α-esterase and monooxygenase activities (3.4-fold and 2.54-fold, respectively) in exposed females of Ae. albopictus compared to the unexposed cohort. Overall, the low resistance levels observed underscore the need for sustained insecticide resistance monitoring and management to maintain the effectiveness of insecticide-based vector control strategies in Nigeria.