Interruption of Chemical Mosquito Control and Evolution of Insecticide Resistance Genes inCulex pipiens(Diptera: Culicidae)

Abstract

Within the Llobregat Delta (Barcelona, Spain), Culex pipiens L. has been the target of organophosphate insecticide (OP) control for 10 yr (1982-1992). Between 1991 and 1992, OPs were replaced by Bacillus-based toxins in all the mosquito control programs within > 150 km of this area. The distribution of several OP-resistance genes was surveyed within the Llobregat Delta and neighboring populations (< 25 km) during the 2 yr following this regional pesticide change to investigate how the change in selection pressure affected the dynamics of OP-resistance genes. The immigration failure of the A2-B2 resistant esterases and the observed difference in OP-resistance dynamics between isolated and nonisolated populations may indicate fitness disadvantages associated with OP-resistance genes, hence a tendency for a decrease in OP-resistance. In contrast, one OP-resistance gene further increased in frequency, whereas the frequencies of some others were maintained. These unexpected results question the importance of pesticides from sources other than mosquito control, and the variability of pleiotropic fitness costs among pesticide resistance genes.

Insecticide resistance in the mosquito Culex pipiens: What have we learned about adaptation?

“…The spread of resistance genes has occurred independently in all treated areas, and in the regions where detailed monitoring was conducted (e.g., southern France, Catalonia, north-eastern Italy and California), it was observed that repetitive spreads at the same locus were taking place (Raymond et al, 1987;Severini et al, 1997;Guillemaud et al, 1998;Lenormand et al, 1998a;Eritja & Chevillon, 1999). Thus it seems that the spread of advantageous mutations is rather common for this example of environmental change in a large population, which is to be considered within the current controversy concerning the phase three of Wright's shifting balance theory (Coyne, Barton & Turelli, 1997).…”

Multiple duplications of the rare ace-1 mutation F290V in Culex pipiens natural populations

“…This strongly suggests that the F290V substitution was originally selected by some specific insecticide molecules. Unfortunately, historical data concerning molecules used in control are difficult to obtain and selection could also be due to pesticides used against agricultural pests (Eritja and Chevillon, 1999;Mouchet, 1988). Thus, the low frequency of the F290V alleles could be explained by current use of insecticides that weakly select it.…”

“…For example, previous surveys in Tunisia revealed many distinct resistance mechanisms at high frequency and it is believed that they are associated to a broad use of a large array of insecticides (Ben Cheikh et al, 2009). In such a context, the rarity of the F290V substitution could be due to a competition with the G119S allele, which confers resistance to a larger spectrum of molecules , or with another resistant gene such as the Ester gene coding detoxifying carboxylesterases and also known to be largely spread in all the studied countries [Cyprus (Wirth, 1998), Spain (Eritja and Chevillon, 1999), Tunisia (Ben Cheikh et al, 2009)] and Lebanon (unpublished data).…”

“…pipiens samples from Spain and Tunisia have been used for other investigations and the characteristics and localization of breeding sites can be found in Eritja andChevillon (1999) andBen Cheikh et al (2009), respectively. Samples from Algeria were collected in 2006 and 2008 from nine breeding sites in a 75 kmwide area along the Mediterranean coast, extending from the western to the eastern borders.…”

Phenotypic effects of concomitant insensitive acetylcholinesterase ( ace-1 R ) and knockdown resistance ( kdr R ) in Anopheles gambiae : a hindrance for insecticide resistance management for malaria vector control

“…Until now, pyrethroids are the only insecticide class recommended for treating mosquito nets because of their excito-repellent properties, efficacy at low-doses, and good tolerance in humans and other mammals [24]. ITNs have been used on a large scale in the last decade but pyrethroids resistance in anopheline mosquitoes were reported in all sub-Saharan Africa [25][26][27][28][29].…”