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

<p>Abstract</p> <p>Background</p> <p>Insecticide resistance is a rapid and recent evolutionary phenomenon with serious economic and public health implications. In the mosquito <it>Anopheles gambiae s.s</it>., 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 (<it>ace-1</it>), potentially associated to a lower fitness cost, recently appeared in <it>An. gambiae</it>.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>The duplicated allele, <it>Ag</it>-<it>ace-1</it>^<it>D</it>, reaches a frequency up to 0.65 in Ivory Coast and Burkina Faso, and is potentially present in Benin. A previous study showed that <it>Ag</it>-<it>ace-1</it>^<it>D</it>, 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.</p> <p>Conclusion</p> <p>The spread of this less costly resistance allele could represent a major threat to public health, as it may impede <it>An. gambiae </it>control strategies, and thus increases the risk of malaria outbreaks.</p

Structure génétique des cécidomyies des céréales en Tunisie

Genetic structure of Hessian flies in Tunisia. The genetic structure of M. destructor and M. hordei was investigated by sampling 21 fields of cereals in 14 localities of central and southern Tunisia. As previously shown, there was no strict association between the cereal species (wheat, barley and oat) and the Mayetiola species. M. destructor males displayed no heterozygosity at the Pgm3 locus, indicating that they were hemizygous as is the PGM locus in North America. In M. hordei, heterozygous males were observed at all loci, but strong heterozygote deficits were found at two loci (Mdh2 et Hk). Since no such deficit was observed in females, the population structure of M. hordei was studied only in females. Although heterozygosity was two fold higher in M. hordei than in M. destructor, the two species were similar for other genetic characteristics, including a low (Fst < 0.05) but significant (P < 0.05) genetic differentiation, no isolation by distance, and similar rates of gene flow (5.7 ≤ Nm ≤ 9.6). These results are discussed in relation to their consequences in the event of controlling Tunisian Hessian flies using wheat cultivars that are resistant to a M. destructor biotype

Étude de la résistance au chlorpyrifos à partir de quelques souches du moustique Culex pipiens L. du sud de la France

International audienc

Cytoplasmic Incompatibility as a Means of Controlling Culex pipiens quinquefasciatus Mosquito in the Islands of the South-Western Indian Ocean

The use of the bacterium Wolbachia is an attractive alternative method to control vector populations. In mosquitoes, as in members of the Culex pipiens complex, Wolbachia induces a form of embryonic lethality called cytoplasmic incompatibility, a sperm-egg incompatibility occurring when infected males mate either with uninfected females or with females infected with incompatible Wolbachia strain(s). Here we explore the feasibility of the Incompatible Insect Technique (IIT), a species-specific control approach in which field females are sterilized by inundative releases of incompatible males. We show that the Wolbachia wPip(Is) strain, naturally infecting Cx. p. pipiens mosquitoes from Turkey, is a good candidate to control Cx. p. quinquefasciatus populations on four islands of the south-western Indian Ocean (La Réunion, Mauritius, Grande Glorieuse and Mayotte). The wPip(Is) strain was introduced into the nuclear background of Cx. p. quinquefasciatus mosquitoes from La Réunion, leading to the LR[wPip(Is)] line. Total embryonic lethality was observed in crosses between LR[wPip(Is)] males and all tested field females from the four islands. Interestingly, most crosses involving LR[wPip(Is)] females and field males were also incompatible, which is expected to reduce the impact of any accidental release of LR[wPip(Is)] females. Cage experiments demonstrate that LR[wPip(Is)] males are equally competitive with La Réunion males resulting in demographic crash when LR[wPip(Is)] males were introduced into La Réunion laboratory cages. These results, together with the geographic isolation of the four south-western Indian Ocean islands and their limited land area, support the feasibility of an IIT program using LR[wPip(Is)] males and stimulate the implementation of field tests for a Cx. p. quinquefasciatus control strategy on these islands

Résistance aux médicaments et aux pesticides (biocides)

Seminaire de prospective scientifique et de lancement du Programme de recherche du Plan national Santé Envitonnement du du Plan Santé travail. Document d'orientation scientifique. Paris 31 mars et 1er avril 2005. ANR, Ministère Délégué à la rechercheThe progress of the health of human populations in the 20th century is largely due to development and the marketing of biocides (drugs and pesticides). Biocides limit the proliferation of unwanted organisms (viruses, bacteria, protozoa or metazoa) or even cells (as in cancer). They include anti-bacterial, anti-parasitic, anti-cancer compounds, as well as pesticides (insecticides and herbicides, for example). The efficiency of a large number of biocides is now compromised by the emergence of resistance phenomena, i. e. the capacity of the target organisms to survive in the presence of normally lethal concentrations of biocide. Knowing that crop pests are responsible for more than 30% of the loss of agricultural production, that infectious diseases are responsible for a third of the annual global mortality, and that more than 95% of failures to anti-cancer treatments are attributed to resistance, it is clear that resistance to biocides are an important concern in public health and agronomy. One of the challenges of the future is to avoid or limit the negative impact of resistance. Here we briefly describe (1) the context of resistance phenomena (origin of resistance: an adaptive process; nature of resistance genes; selection pressures and fitness; evolution of resistance and unknown factors; strategies to control resistance), (2) the scientific dynamics, and (3) the scientific perspectives and priorities (understanding of mechanisms and dynamics of resistance; development of new biocides; society and resistance

Insecticide resistance genes in mosquitoes: Their mutations, migration, and selection in field populations

International audienceInsecticides have been used intensively to control insect populations over the last 50 years and many species of insects have developed resistance to several families of insecticides, These resistances are mainly due to two mechanisms: mutation of the insecticide target protein (leading to a decrease in its affinity for the concerned insecticide family), and increased detoxification, Recent molecular studies suggest that the mutations conferring resistance are rare and sometimes unique events in any given species, The wide geographic distribution of some of these genes can then only be explained by the balance between migration and selection at the population level