Ace-1 duplication in Anopheles gambiae: a challenge for malaria control

Luc Djogbénou,Pierrick Labbé,Fabrice Chandre,Mylène Weill,Nicole Pasteur

doi:10.1186/1475-2875-8-70

Abstract

BackgroundInsecticide resistance is a rapid and recent evolutionary phenomenon with serious economic and public health implications. In the mosquito Anopheles gambiae s.s., main vector of malaria, resistance to organophosphates and carbamates is mainly due to a single amino-acid substitution in acetylcholinesterase 1 (AChE1). This mutation entails a large fitness cost. However, a resistant duplicated allele of the gene encoding AChE1 (ace-1), potentially associated to a lower fitness cost, recently appeared in An. gambiae.MethodsUsing molecular phenotype data collected from natural populations from West Africa, the frequency of this duplicated allele was investigated by statistical inference. This method is based on the departure from Hardy-Weinberg phenotypic frequency equilibrium caused by the presence of this new allele.ResultsThe duplicated allele, Ag-ace-1D, reaches a frequency up to 0.65 in Ivory Coast and Burkina Faso, and is potentially present in Benin. A previous study showed that Ag-ace-1D, present in both M and S molecular forms in different West Africa countries, was generated by a single genetic event. This single origin and its present distribution suggest that this new allele is currently spreading.ConclusionThe spread of this less costly resistance allele could represent a major threat to public health, as it may impede An. gambiae control strategies, and thus increases the risk of malaria outbreaks.

Highlights

Insecticide resistance is a rapid and recent evolutionary phenomenon with serious economic and public health implications
The frequency of the recently discovered duplicated allele of the ace-1 gene in An. gambiae, Ag-ace-1D, was investigated in natural populations from West Africa by considering the departure from Hardy-Weinberg proportions caused by its presence [6]
Insecticides for controlling malaria vectors are a major weapon in the battle between humans and malaria

Summary

Introduction

Insecticide resistance is a rapid and recent evolutionary phenomenon with serious economic and public health implications. In the mosquito Anopheles gambiae s.s., main vector of malaria, resistance to organophosphates and carbamates is mainly due to a single amino-acid substitution in acetylcholinesterase 1 (AChE1). This mutation entails a large fitness cost. In the arms race between arthropods and humans, the mosquito Anopheles gambiae, the main vector of malaria, seems to have just moved up a gear with the emergence of a resistant duplicated allele of the gene encoding acetylcholinesterase 1 (AChE1). Heterozygotes are subject to smaller costs than resistant homozygotes in the absence of insecticide In treated areas, they survive better than susceptible homozygotes, but are less resistant than ace-1R homozygotes. Heterozygotes cannot invade due to the segregation burden leading to the loss of the advantage in half of their progeny

Methods

Results

Conclusion