Background: The insecticide resistance profile of the malaria vector Anopheles funestus and its underlying mechanisms remain poorly characterized in several regions of Senegal. To address this gap in knowledge, we investigated insecticide resistance profiles and assessed the contribution of metabolic resistance in Anopheles funestus populations from central Senegal. Methods: Indoor-resting blood-fed and gravid female mosquitoes were collected from randomly selected human dwellings in each study site using mouth aspirators. WHO susceptibility tests, Piperonyl butoxide (PBO) synergist assays, and resistance intensity assays were conducted on unfed 3-5-day-old F1 female progeny derived from wild-caught blood-fed Anopheles funestus females. Four classes of public health insecticides were tested. Results: Anopheles funestus populations from Camara, Keur Mamadou, and Tawa Mboudaye showed moderate to high resistance intensity to pyrethroids, whereas populations from Dielmo exhibited low intensity to lambda-cyhalothrin and moderate intensity to alpha-cypermethrin. Moderate resistance to bendiocarb was detected in Nioro, but neither in Sokone nor Ndoffane. Overall, populations remained susceptible to largely susceptible to the organochlorine (DDT) and organophosphates across the study areas. However, in the localities of Tawa Mboudaye and Keur Mamadou, resistance to fenitrothion (86.4% and 76.1% mortality, respectively) and suspected resistance to DDT (91.4% and 88.3% mortality, respectively) were observed. PBO synergist assays suggest the involvement of cytochrome P450 monooxygenases mediating resistance to pyrethroids and bendiocarb. Conclusions: This study demonstrates that Anopheles funestus populations in central Senegal exhibit moderate to high levels of pyrethroid resistance, together with localized resistance to bendiocarb and fenitrothion in some locations. The results suggest that metabolic resistance mechanisms, particularly those involving cytochrome P450 monooxygenases, may contribute substantially to the observed resistance phenotypes; however, these findings provide only indirect evidence, and additional mechanisms beyond P450s cannot be excluded, especially for compounds such as DDT and bendiocarb. These results support the consideration of PBO-based LLIN deployment across the study areas.
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