The G119S Acetylcholinesterase (Ace-1) Target Site Mutation Confers Carbamate Resistance in the Major Malaria Vector Anopheles gambiae from Cameroon: A Challenge for the Coming IRS Implementation

摘要

Growing resistance is reported to carbamate insecticides in malaria vectors in Cameroon. However, the contribution of acetylcholinesterase ( ) to this resistance remains uncharacterised. Here, we established that the mutation is driving resistance to carbamates in populations from Cameroon. Insecticide bioassay on field-collected mosquitoes from Bankeng, a locality in southern Cameroon, showed high resistance to the carbamates bendiocarb (64.8% ± 3.5% mortality) and propoxur (55.71% ± 2.9%) but a full susceptibility to the organophosphate fenitrothion. The TaqMan genotyping of the mutation in field-collected adults revealed the presence of this resistance allele (39%). A significant correlation was observed between the and carbamate resistance at allelic ((bendiocarb; odds ratio (OR) = 75.9; < 0.0001) and (propoxur; OR = 1514; < 0.0001)) and genotypic (homozygote resistant vs. homozygote susceptible (bendiocarb; OR = 120.8; < 0.0001) and (propoxur; OR = 3277; < 0.0001)) levels. Furthermore, the presence of the mutation was confirmed by sequencing an portion flanking codon 119. The cloning of this fragment revealed a likely duplication of in Cameroon as mosquitoes exhibited at least three distinct haplotypes. Phylogenetic analyses showed that the predominant allele is identical to that from West Africa suggesting a recent introduction of this allele in Central Africa from the West. The spread of this represents a serious challenge to future implementation of indoor residual spraying (IRS)-based interventions using carbamates or organophosphates in Cameroon.