First Incidence of CYP9K1, CYP6P4 and CYP6Z1 in Anopheles gambiae ss from Nigeria

Background: Anopheles resistance to insecticides is an impediment to the success of malaria control programmes in sub-Saharan Africa. This study addresses the enzymes that play the key role in insecticide resistance in Kogi State, Nigeria.Methods: Anopheles immature stages were collected from breeding sites across four LGAs in Kogi State, Nigeria. Adult anophelines were identified morphologically and molecularly to species level using the polymerase chain reaction. Adult Anopheles mosquitoes were exposed to eight different insecticides belonging to organochlorine, organophosphate, carbamate and pyrethroids. Newly developed and integrable to the LabDisk automated diagnostic platform quantitative Reverse Transcription-real-time PCR (qRT-PCR) 3-plex TaqMan® assays were used to quantify 7 detoxification genes’ expression. Fold-changes, 95% CIs and statistical significance were performed according to the Pfaffl methods. Results: An. gambiae sl were susceptible to pirimiphos methyl in all the LGAs, but resistance to alphacypermethrin, permethrin, DDT, bendiocarb, propoxur, lambdacyhalothrin and deltamethrin. The detoxification genes CYP6P3(1.6), CYP6M2(36 folds), CYP9K1(6.4 folds), CYP6P4(5.3), CYP6Z1(4.8 folds), GSTE2(4.1 fold), CYP6P1(0.50 folds) and CYP4G16 (2.36 folds) were encountered but only CYP6M2, CYP9K1, CYP6P4 and CYP6Z1 were found to be up regulated in the Dekina multi resistant (pyrethroids, DDT, bendiocarb) population compared to two susceptible (Kisumu and G3) laboratory strains. Resistance was observed in seven out of the eight insecticides tested. Very high level of resistance was observed in DDT across the three LGAs. The CYP6M2, CYP9K1, CYP6P4 and CYP6Z1 were up regulated genes that confer resistance to different insecticides. Conclusion: This study recorded for the first time CYP9K1, CYP6P4 and CYP6Z1 detoxification genes in wild Anopheles gambiae ss populations from Nigeria. In light of the absence of iAche mutations in our results, carbamate (bendiocarb and propoxur) resistance could be associated with the expression of CYP6P4 that has been previously implicated.