Evidence of intensification of Pyrethroid Resistance in the major Malaria Vectors in Kinshasa, Democratic Republic of Congo

Abstract Assessing patterns and evolution of insecticide resistance in malaria vectors is a prerequisite to design suitable control strategies. Here, we characterised resistance profile in Anopheles gambiae and Anopheles funestus in Kinshasa and assess the level of aggravation by comparing to previous 2015 estimates. Both species collected in July 2021 were highly resistant to pyrethroids at 1X, 5X and 10X concentrations (mortality < 90%) and remain fully susceptible to bendiocarb and pirimiphos methyl. Partial recovery of susceptibility was observed in An. gambiae after PBO synergist assays for both permethrin and α-cypermethrin with total recovery of susceptibility observed for deltamethrin compared to 2015, the efficacy of bednets decreased significantly in 2021, for the most of nets. Genotyping of resistance markers revealed a near fixation of the L1014-Kdr mutation (98.3%) in An. gambiae in 2021. The frequency of the 119F-GSTe2 resistant significantly increased between 2015 and 2021 (19.6% vs 33.3%; P = 0.02) in An. funestus . Transcriptomic analysis also revealed a significant increased expression (P < 0.001) of key cytochrome P450s in An. funestus notably CYP6P9a . The escalation of pyrethroid resistance observed in Anopheles populations from Kinshasa coupled with increased frequency/expression level of resistance genes highlights an urgent need to implement tools to improve malaria vector control.