Kdr Resistance Gene and Spatial Distribution of Anopheles gambiae Complex Members in a Secondary City in Central Africa: Ayos Case (South Cameroon)

The study was conducted in December 2019 and February 2020 in two areas of Ayos city, Akoun (urban site) and Ebabodo (peri-urban site), in order to study the spatial distribution of members of the Anopheles gambiae complex, to determine their resistance status and to investigate the occurrence and distribution of the Kdr mutation. Mosquitoes were collected at the larval stage using the dipping method and then reared to the adult stage. The susceptibility of adult populations of An. gambiae s.l. to DDT and pyrethroids was assessed according to the WHO recommended protocol. Mosquitoes from the tests were identified by SINE PCR. Only test survivors were used for Kdr mutation testing by PCR. In the study sites, the gambiae complex was composed of An. coluzzii and An. gambiae living in sympatry in their oviposition sites with a predominance of An. coluzzii in Akoun (90.83%) and Ebabodo (76.69%). Tests with deltamethrin, permethrin and DDT revealed mortality rates of less than 70% whatever the locality of origin of the anopheles. Diagnostic PCR for the Kdr mutation showed that 100% of the survivors had the mutation in both sites, with frequencies of the resistant allele of 1.0 in both species. The high resistance of An. coluzzii and An. gambiae to insecticides requires the development of new insecticidal molecules.