High incidence of ace-1 duplicated haplotypes in resistant Culex pipiens mosquitoes from Algeria

The status of genes conferring resistance to organophosphate and carbamate insecticides has been examined in Culex pipiens pipiens mosquitoes sampled in Algeria. Presence of overproduced esterases was sporadic, but acetylcholinesterase-1 resistant alleles were observed in almost all samples. We focused our study on the AChE1 G119S substitution characterized in almost all samples, mostly at the heterozygous state. A genetic test revealed the presence of ace-1 duplication associating a susceptible and a resistant ace-1 copy. Molecular characterization showed a high occurrence of ace-1 duplication with six distinct duplicated alleles out of four samples. The inferred frequency of duplicated allele suggests that it is replacing the single resistant G119S allele. Finally, we discuss the mechanism at the origin of these duplicated haplotypes and their consequences on the management of insecticide resistance.

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► Target site insensitive acetylcholinesterase-1 was frequently observed in Algeria.
► The predominant G119S AChE1 allele was found mostly in the heterozygous state.
► Molecular characterization showed a high occurrence of ace-1 duplication.
► Inferred frequency of duplicated allele suggests an ongoing allele replacement.
► Duplicated ace-1 allele may incur a reduced fitness cost compared to non-duplicated allele.