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Background: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,Plasmodiuminfection rate, insecticide resistance profiles and underlying resistance mechanisms.Methods: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 F1adults. 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 andPlasmodiuminfection rates were investigated.Results:Anopheles funestuss.s. was the most abundant species in Elende (85%) followed byAnopheles gambiaes.s. (15%) with both having similar sporozoite rate. Both species exhibited high levels of resistance to the pyrethroids, permethrin and deltamethrin (An. gambiaes.s. was resistant to DDT (9.9% mortality) and bendiocarb (54% mortality) while susceptible to organophosphate.An. funestuss.s. was resistant to dieldrin (1% mortality), DDT (86% mortality) but susceptible to carbamates and organophosphates. The L119F-GSTe2 resistance allele (8%) and G119Sace-1 resistance allele (15%) were detected inAn. funestuss.s. andAn. gambiaes.s., respectively.Furthermore, the high pyrethroid/DDT resistances inAn. gambiaecorresponded with an increase frequency of 1014Fkdrallele (95%). Transcriptional profiling of candidate cytochrome P450 genes reveals the over-expression ofCYP6P5,CYP6P9aandCYP6P9b.Conclusion:The resistance to multiple insecticide classes observed in these vector populations alongside the significantPlasmodiumsporozoite rate highlights the challenges that vector control programs encounter in sustaining the regular benefits of contemporary insecticide-based control interventions in forested areas.

Background:Insecticides resistance inAnophelesmosquitoes limits Long-Lasting Insecticidal Nets (LLIN) used for malaria control in Africa, especially Benin. This study aimed to evaluate the bio-efficacy of current LLINs in an area whereAn. funestuss.l.andAn. gambiaehave developed multi-resistance to insecticides, and to assess in experimental huts the performance of a mixed combination of pyrethroids and piperonyl butoxide (PBO) treated nets on these resistant mosquitoes.Methods:The study was conducted at Kpomè, Southern Benin. The bio-efficacy of LLINs againstAn. funestus and An. gambiaewas assessed using the World Health Organization (WHO) cone and tunnel tests. A released/recapture experiment following WHO procedures was conducted to compare the efficacy of conventional LLINs treated with pyrethroids only and LLINs with combinations of pyrethroids and PBO. Prior to huts trials, we confirmed the level of insecticide and PBO residues in tested nets using high performance liquid chromatography (HPLC).Results:Conventional LLINs (Type 2 and Type 4) have the lowest effect against local multi-resistantAn. funestus s.s. and An. coluzziipopulations from Kpomè. Conversely, when LLINs containing mixtures of pyrethroids and PBO (Type 1 and Type 3) were introduced in trial huts, we recorded a greater effect against the two mosquito populations (P < 0.0001). Tunnel test withAn. funestus s.s.revealed mortalities of over 80% with this new generation of LLINs (Type 1 and Type 3),while conventional LLINs produced 65.53 ± 8.33% mortalities for Type 2 and 71.25 ±7.92% mortalities for Type 4. Similarly, mortalities ranging from 77 to 87% were recorded with the local populations ofAn. coluzzii.Conclusion:This study suggests the reduced efficacy of conventional LLINs (Pyrethroids alone) currently distributed in Benin communities whereAnophelespopulations have developed multi-insecticide resistance. The new generation nets (pyrethroids+PBO) proved to be more effective on multi-resistant populations of mosquitoes.