Multiple insecticide resistance and infection in the principal malaria vectors and in a forested locality close to the Yaoundé airport, Cameroon.

Reducing the burden of malaria requires better understanding of vector populations, particularly in forested regions where the incidence remains elevated. Here, we characterized malaria vectors in a locality near the Yaoundé international airport, Cameroon, including species composition, abundance, infection rate, insecticide resistance profiles and underlying resistance mechanisms. Blood-fed adult mosquitoes resting indoors were aspirated from houses in April 2019 at Elende, a locality situated 2 km from the Yaoundé-Nsimalen airport. Female mosquitoes were forced to lay eggs to generate F adults. Bioassays were performed to assess resistance profile to the four insecticides classes. The threshold of insecticide susceptibility was defined above 98% mortality rate and mortality rates below 90% were indicative of confirmed insecticide resistance. Furthermore, the molecular basis of resistance and infection rates were investigated. s.s. was the most abundant species in Elende (85%) followed by s.s. (15%) with both having similar sporozoite rate. Both species exhibited high levels of resistance to the pyrethroids, permethrin and deltamethrin (<40% mortality). s.s. was resistant to DDT (9.9% mortality) and bendiocarb (54% mortality) while susceptible to organophosphate. s.s. was resistant to dieldrin (1% mortality), DDT (86% mortality) but susceptible to carbamates and organophosphates. The L119F-GSTe2 resistance allele (8%) and G119S -1 resistance allele (15%) were detected in s.s. and s.s., respectively Furthermore, the high pyrethroid/DDT resistances in corresponded with an increase frequency of 1014F allele (95%). Transcriptional profiling of candidate cytochrome P450 genes reveals the over-expression of , and The resistance to multiple insecticide classes observed in these vector populations alongside the significant sporozoite rate highlights the challenges that vector control programs encounter in sustaining the regular benefits of contemporary insecticide-based control interventions in forested areas.