Ace-1 duplication in Anopheles gambiae: a challenge for malaria control.
BACKGROUND
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. However, a resistant duplicated allele of the gene encoding AChE1 (ace-1), potentially associated to a lower fitness cost, recently appeared in An. gambiae.


METHODS
Using 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.


RESULTS
The duplicated allele, Ag-ace-1(D), 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-1(D), 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.


CONCLUSIONS
The 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.
Djogbénou
Luc
L
Institut de Recherche pour le Développement, UR 016, Cotonou, Benin. Luc.Djogbenou@ird.fr
Labbé
Pierrick
P
Chandre
Fabrice
F
Pasteur
Nicole
N
Weill
Mylène
M
D000110:Acetylcholinesterase / Q000235:genetics* / Q000378:metabolism; D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D000852:Anopheles / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D020440:Gene Duplication / Q000187:drug effects; D005787:Gene Frequency / Q000187:drug effects; D005828:Genetics, Population; D005838:Genotype; D007303:Insect Vectors / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides; D008969:Molecular Sequence Data; D009032:Mosquito Control; D009154:Mutation / Q000187:drug effects / Q000235:genetics
D007306:Insecticides; D000110:Acetylcholinesterase