Abstract
BackgroundChanges in the natural habitats of insect groups are determined the genetic polymorphisms between individuals. The objective of this study was to establish the genetic structure of the Anopheles coluzzii populations in four localities of Benin.MethodsInsecticide surveys and larval sampling were conducted on 4 study localities, including Cotonou, Ketou, Zagnanado, and Sô-Ava. Molecular characterizations were performed on the Anopheles mosquitoes collected with the allelic and genotypic frequencies of kdr gene determined. The multiple comparison Chi square test for proportions was performed with R version 3.3.3. Next, the observed heterozygosity, expected heterozygosity, and indices of fixation, and genetic differentiation were estimated. Finally, the Hardy–Weinberg equilibrium (EHW) was determined to assess whether panmixia exists in the different populations of mosquitoes of the agroecological zones under study.ResultsCarbamates, pyrethroids, organophosphorus and organochlorines use have been reported in all localities except Sô-Ava. Anopheles coluzzii was strongly represented across all study localities. The L1014F allele was observed in the localities of Kétou, Cotonou and Zagnanado. Likewise, insecticide selection pressure of homozygous resistant individuals (L1014F/L1014F) was significantly higher in Kétou, Cotonou and Zagnanado (p value < 0.05). Surprisingly in Sô-Ava, a relatively high frequency of the L1014F allele despite the reported absence of pesticide use was observed. All mosquito populations were found to be deficient in heterozygosity across the study sites (FIS< 0). No genetic differentiation (FST< 0) was observed in the localities of Zagnanado and Kétou.ConclusionThe survey on the use of insecticides showed that insecticide selection pressures differ across the investigated localities. It would be desirable to rotate or apply formulations of combined products with different modes of action. Doing so would enable a better management of resistant homozygous individuals, and mitigate the resistance effect of commonly used insecticides.
Highlights
Changes in the natural habitats of insect groups are determined the genetic polymorphisms between individuals
A lack of adequate water drainage system and an excessive distortion of the natural terrain due to human dwellings and community infrastructure may promote the emergence of mosquito breeding sites that are suitable environments for the reproduction of malaria vectors, the emergence of adult mosquitoes and subsequently promote human-vector contact [8]
In the Republic of Benin, several studies have confirmed the role of pesticides in the development of insecticide resistance in An. gambiae [11, 12]
Summary
Changes in the natural habitats of insect groups are determined the genetic polymorphisms between individuals. Agricultural fields are very good breeding sites for malaria vectors as they contribute to the selection of resistant individuals due to the uncontrolled use of multiple pesticides [9]. The massive use of insecticides in agriculture [14] and in public health [15, 16] is the main driver of the development of insecticide resistance in malaria vectors [17]. To this day, two main mechanisms are known to be involved in metabolic resistance to insecticides in mosquitoes. The mutations on the voltage-gated sodium channel gene that are the targets of pyrethroids, and the overproduction of detoxifying enzymes are the main mechanisms of mosquito resistance to insecticide [18,19,20]
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