Genes (Oct 2019)

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

  • Emmanuel Elanga-Ndille,
  • Lynda Nouage,
  • Cyrille Ndo,
  • Achille Binyang,
  • Tatiane Assatse,
  • Daniel Nguiffo-Nguete,
  • Doumani Djonabaye,
  • Helen Irving,
  • Billy Tene-Fossog,
  • Charles S. Wondji

DOI
https://doi.org/10.3390/genes10100790
Journal volume & issue
Vol. 10, no. 10
p. 790

Abstract

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Growing resistance is reported to carbamate insecticides in malaria vectors in Cameroon. However, the contribution of acetylcholinesterase (Ace-1) to this resistance remains uncharacterised. Here, we established that the G119S mutation is driving resistance to carbamates in Anopheles gambiae 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 G119S mutation in field-collected adults revealed the presence of this resistance allele (39%). A significant correlation was observed between the Ace-1R and carbamate resistance at allelic ((bendiocarb; odds ratio (OR) = 75.9; p < 0.0001) and (propoxur; OR = 1514; p < 0.0001)) and genotypic (homozygote resistant vs. homozygote susceptible (bendiocarb; OR = 120.8; p < 0.0001) and (propoxur; OR = 3277; p < 0.0001)) levels. Furthermore, the presence of the mutation was confirmed by sequencing an Ace-1 portion flanking codon 119. The cloning of this fragment revealed a likely duplication of Ace-1 in Cameroon as mosquitoes exhibited at least three distinct haplotypes. Phylogenetic analyses showed that the predominant Ace-1R 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 Ace-1R represents a serious challenge to future implementation of indoor residual spraying (IRS)-based interventions using carbamates or organophosphates in Cameroon.

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