Assogba_2014_Parasit.Vectors_7_548

BackgroundMalaria is endemic in sub-Saharan Africa with considerable burden for human health. Major insecticide resistance mechanisms such as kdr R and ace-1 R alleles constitute a hindrance to malaria vector control programs. Anopheles gambiae bearing both kdr and ace-1 resistant alleles are increasingly recorded in wild populations. In order to maintain the efficacy of vector control strategies, the characterization of concomitant kdr and ace-1 resistance, and their pleiotropic effects on malaria vector phenotype on insecticide efficacy are important.MethodsLarval and adult bioassays were performed with different insecticide classes used in public health following WHO standard guidelines on four laboratory Anopheles gambiae strains, sharing the same genetic background but harboring distinct resistance status: KISUMU with no resistance allele; ACERKIS with ace-1 R allele; KISKDR with kdr R allele and ACERKDRKIS with both resistance alleles inverted question mark ace-1 R and kdr R .ResultsLarval bioassays indicate that the homozygote resistant strain harboring both alleles (ACERKDRKIS) displayed slightly but significantly higher resistance level to various insecticides like carbamates (bendiocarb, p inverted question mark< inverted question mark0.001; propoxur, p inverted question mark= inverted question mark0.02) and organophosphates (chlorpyriphos-methyl, p inverted question mark= inverted question mark0.002; fenitrothion, p inverted question mark< inverted question mark0.001) when compared to ACERKIS strain. However, no differences were recorded between ACERKDRKIS and KISKDR resistance level against permethrin (Pyrethroid, p inverted question mark= inverted question mark0.7) and DDT (Organochlorine, p inverted question mark= inverted question mark0.24). For adult bioassays, the percentages of mosquitoes knocked down were significantly lower for ACERKDRKIS than for KISKDR with permethrin (p inverted question mark= inverted question mark0.003) but not with deltamethrin. The percentage of mortality from adult bioassays was similar between ACERKDRKIS and ACERKIS with carbamates and organophosphates, or between ACERKDRKIS and KISKDR with pyrethroid and DDT. Concerning acetylcholinesterase enzyme, ACERKDRKIS strain showed similarAChE1 activity than that of ACERKIS.ConclusionThe presence of both kdr R and ace-1 R alleles seems to increase the resistance levels to both carbamate and organophosphate insecticides and at operational level, may represent an important threat to malaria vector control programs in West Africa.