Comparative Resistance and Knockdown Dynamics of Anopheles gambiae and Anopheles funestus to Alphacypermethrin in Northern Nigeria

Abstract

Insecticide resistance among malaria vectors continues to undermine the effectiveness of pyrethroid-based interventions such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Alphacypermethrin, a widely deployed pyrethroid, has shown reduced efficacy against key malaria vectors, particularly Anopheles gambiae and Anopheles funestus. This study comparatively assessed the resistance status and knockdown dynamics of these two species in malaria-endemic communities in Northern Nigeria. This study compared the resistance status of Anopheles gambiae and Anopheles funestus to alphacypermethrin, assessed knockdown rates over time, and identified mosquito species using morphological characteristics and molecular identification. Adult female mosquitoes were collected from malaria-endemic communities using standard collection methods. Species identification was carried out morphologically using standard taxonomic keys and by molecular identification. Susceptibility tests were conducted using World Health Organization (WHO) standard bioassay procedures with alphacypermethrin-impregnated papers. Knockdown was recorded at 10-minute intervals for 60 minutes, while mortality was assessed after 24 hours. Data were analyzed using descriptive statistics and probit analysis. Both Anopheles gambiae and Anopheles funestus populations exhibited varying levels of resistance to alphacypermethrin. Anopheles gambiae demonstrated a higher resistance profile, with reduced and delayed knockdown compared to Anopheles funestus. Knockdown increased progressively with exposure time in both species; however, Anopheles funestus showed significantly faster knockdown rates and higher susceptibility. Mortality after 24 hours further confirmed greater tolerance in Anopheles gambiae relative to Anopheles funestus. The findings indicate marked interspecific variation in response to alphacypermethrin, with Anopheles gambiae exhibiting higher resistance than Anopheles funestus. These results highlight the need for continuous insecticide resistance monitoring and strengthened integrated vector management strategies to sustain malaria control efforts in Northern Nigeria.