Entomological surveillance of malaria vector: species, behaviors, and insecticide resistance in southern and central Benin

BACKGROUND: Malaria transmission in Benin is shaped by ecological heterogeneity, vector biting behavior, and increasing insecticide resistance. However, integrated multi-season data combining vector behavior, infection, and resistance remain limited in southern and central Benin. METHODS: From December 2023 to October 2024, an entomological and molecular survey was conducted in six districts across southern and central Benin over dry and rainy season collection rounds. Adult mosquitoes were collected using human landing catches (HLC) and pyrethrum spray catches (PSC), identified morphologically and molecularly, and tested for Plasmodium falciparum infection by qPCR. WHO insecticide susceptibility tests were performed, complemented by molecular analyses of resistance mutations (kdr L1014F and ace-1R G119S). RESULTS: Anopheles gambiae s.l. was the predominant vector (> 98%), exhibiting both indoor and outdoor biting with site- and season-specific heterogeneity. Among indoor-resting females collected by PSC, human blood meals predominated, indicating high anthropophagy in this subset. EIRs were highest in Ifangni and Toffo, including during the dry season. Pyrethroid resistance was widespread, with kdr allele frequencies exceeding 65% in all sites; susceptibility to pirimiphos-methyl was generally higher but reduced mortality was observed in some districts. CONCLUSION: These findings support stratified, locally tailored vector control in southern and central Benin, including deployment of next-generation nets where pyrethroid resistance is intense, IRS guided by site-specific susceptibility profiles and rotation, and larval source management in areas with stable breeding habitats. CLINICAL TRIAL NUMBER: Not applicable.