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Background: The fight against malaria faces various biological obstacles, including the resistance of parasites to anti-malarial drugs and the resistance of mosquito vectors to insecticides. The resistance of Anopheles gambiae sensu lato (s.l.) to pyrethroids, the only class of insecticides used to impregnate mosquito nets, is known in Benin; the expansion of this resistance is influenced by the existence of gene flow between species, otherwise by the presence or absence of the kdr mutation in them. The objective of this study is to determine the spatial distribution of An. gambiae and the level of expression of the pyrethroid resistance kdr gene in seven agro-ecological zones of Benin. Methods: The study was conducted in 18 localities belonging to seven agro-ecological zones where environmental parameters varied. The sites represent the main areas of eco-epidemiological malaria in Benin. Anopheles gambiae larvae were collected in natural breeding sites using ladles and dipping method and reared under standard conditions. These larvae were reared under standard conditions of temperature and humidity (26 to 30 °C and 60 to 90%) at the insectarium of the Centre de Recherche Entomologique de Cotonou (CREC). Adult female mosquitoes having emerged are morphologically and molecularly identified. Homozygous resistant (1014F/1014F), homozygous sensitive (1014L/1014L) and heterozygous (1014F/1014L) genotypes of the L1014Fkdr gene mutation are determined by PCR. Results: A total of 677 An. gambiae was subjected at the PCR. The results revealed the presence of three vector species of the An. gambiae complex, of which 409 Anopheles coluzzii, 259 An.gambiae, 5 hybrids (An. coluzzii/An. gambiae) and 4 Anopheles arabiensis in the different agro-ecological zones. The four An. arabiensis were only found in Dassa, a locality in the cotton zone of central Benin. The frequency of distribution of the L1014F allele of the kdr gene varies from 84.48 to 100% in An. gambiae, from 80 to 100% in An. coluzzii and from 0 to 75% in An. arabiensis in the different agro-ecological zones. Moreover, a significant difference is generally observed in the distribution of the L1014F allele (P < 0.05). By comparing in pairs the distribution frequencies of this allele in the two species by agro-ecological zone, only a significant difference is noted in the central cotton and fishery zones (P = 0.0496). Conclusion: In summary, even if the data are in small portions, the An. Arabiensis species was found only in central Benin and the L1014F allele of the kdr gene is widespread and seems to fix in all the species recorded in the different agro-ecological zones. This situation amplifies the problem of resistance, which could eventually be a significant obstacle for the malaria vectors control. Similarly, a study of their genetic structure via the L1014F allele is necessary in order to put in place strategies to manage this resistance. These strategies will take into account both the ecology and the genetic diversity of the organisms involved to preserve the effectiveness of pyrethroids, the only insecticides used for the impregnation of mosquito nets. [ABSTRACT FROM AUTHOR]

Background: Changes 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. Methods: Insecticide 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. Results: Carbamates, 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. Conclusion: The 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. [ABSTRACT FROM AUTHOR]