Entomological surveys and insecticide resistance in the dengue vector Aedes aegypti in Dakar, Senegal: First detection of the kdr mutation

Aedes aegypti is the primary vector of arboviruses in Senegal, yet this species is not typically targeted by routine vector control programs. Through entomological surveillance, we investigated over a one-year (2022-2023) the risk of arbovirus transmission in Dakar, Senegal, the spatial distribution of insecticide resistance and the underlying resistance mechanisms. Weekly ovitraps were deployed in 15 localities (10 per locality), and monthly adult mosquito collections were conducted in six localities. Arboviruses were detected in adult Ae. aegypti using Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and positive sample were sequenced for phylogenetic analysis to determine the genetic diversity. Blood-feeding preferences and resting behaviors were assessed, and WHO tube bioassays evaluated susceptibility to pyrethroids, organophosphates, and carbamates. Molecular screening targeted knockdown resistance (kdr) mutations (F1534C, V1016G/I, S989P). Ovitrap positivity peaked between August and October, coinciding with the rainy season. Ae. aegypti was detected in all surveyed localities, and dengue virus (DENV) was found in adult mosquitoes between September and December 2022, confirming active transmission risk. Females predominantly fed on humans and were found resting both indoors and outdoors. All tested populations were resistant to permethrin and bendiocarb, with suspected resistance to malathion. kdr mutations of F1534C (CC, FC), V1016G (VG), S989P (SP, and PP) were detected. These findings demonstrate a substantial entomological risk of arbovirus transmission in Dakar, characterized by high vector density, confirmed DENV infection, and widespread insecticide resistance. In this study, we detected three kdr mutations (F1534C, V1016G, and S989P), while previous studies in Senegal have documented metabolic resistance mechanisms. Together, these resistance mechanisms may compromise the efficacy of vector control strategies. Integrated vector management combining rational insecticide use, source reduction, and innovative control tools is recommended for sustainable Aedes-borne disease control in Senegal.