Susceptibility of the chlorfenapyr on wild populations of Anopheles gambiae s.l. resistant to pyrethroids along the south–north transect of Benin

Abstract Background The intensity and spread of resistance of Anophele s populations to traditional neurotoxic insecticides pose a considerable threat to vector control tools. This resistance has led to the search for new classes of insecticides with a different mode of action. Thus, this study aimed to collect data on the susceptibility of An. gambiae s.l . to chlorfenapyr, a pyrrole insecticide in several communes of the south–north transect of Benin. Methods An. gambiae s.l. were collected as larvae and pupae from eight communes located along the south–north transect of Benin and reared to adulthood. Female mosquitoes aged 3–5 days were exposed to pyrethroid-impregnated papers (permethrin, deltamethrin, alphacypermethrin) using WHO tube assays and to chlorfenapyr using the CDC bottle assay. Polymerase chain reaction was used to assess the molecular species composition in the An. gambiae s.l . and the frequency of knockdown resistance ( kdr ) mutations. Results A high level of resistance to pyrethroids was observed at all sites. At all sites, mean mortality was 36.51% with deltamethrin, compared with 83.75% with pre-exposed delthamethrin, representing a 2.29-fold increase in mortality (P < 0.0001). Nevertheless, the different mosquito populations in each commune showed susceptibility to chlorfenapyr with 100% mortality already after 48 h of exposure. Furthermore, An. gambiae s.s. , An. coluzzii and An. arabiensis were species of the Anopheles gambiae s.l. identified in sites, with An. coluzzii (60%) being the most represented, followed by An. gambiae s.s. (27%). Moreover, the west kdr frequency was very high (62 to 100%) in all sites, regardless of the species of the Anopheles gambiae s.l. Conclusion The Anopheles gambiae s.l. populations tested were susceptibility to chlorfenapyr in the north–south transect of Benin despite their high level of resistance to pyrethroids. These results will be very useful for the National Malaria Control Program (NMCP) of Benin in the choice of insecticides according to the control strategy to be implemented.