Insecticide resistance in mosquito vectors

Resistance to insecticides among mosquitoes that act as vectors for malaria (Anopheles gambiae) and West Nile virus (Culex pipiens) emerged more than 25 years ago in Africa, America and Europe; this resistance is frequently due to a loss of sensitivity of the insect's acetylcholinesterase enzyme to organophosphates and carbamates1. Here we show that this insensitivity results from a single amino-acid substitution in the enzyme, which we found in ten highly resistant strains of C. pipiens from tropical (Africa and Caribbean) and temperate (Europe) areas, as well as in one resistant African strain of A. gambiae. Our identification of this mutation may pave the way for designing new insecticides

Quantitative variation and selection of esterase gene amplification in Culex pipiens

International audienceAlthough descriptions of evolutionary mechanisms are common in the literature, very few studies focus on the possible evolution of the adaptive genes themselves, i.e. their quantitative and qualitative changes. Evolution of insecticide resistance in Culex pipiens is a suitable model for studying such processes. In this species, organophosphorous insecticide resistance can be achieved through the overproduction of esterases that sequester the insecticide, and this overproduction can be caused by gent amplification. It is generally assumed, but never verified, that esterase activity, and therefore resistance, is monotonically related to gene amplification. We have analysed resistance, esterase activity and gene amplification in different laboratory strains and natural populations in order to detect variability and to infer effects of selection on these factors. We have shown that resistance, esterase activity and amplification covary, that insecticide selection is able to increase amplification levels, and that a fitness cost is probably attached to the amplification in laboratory strains, related to the level of amplification. The importance of variation in gene amplification level is discussed and some evolutionary implications are proposed