||Genetic structure of Anopheles gambiae s.s populations following the use of insecticides on several consecutive years in southern Benin
Fassinou Arsène Jacques Y. H. ,
Koukpo Come Z. ,
Ossè Razaki A. ,
Agossa Fiacre R. ,
Assogba Benoit S. ,
Sidick Aboubakar ,
Sewadé Wilfrid T. ,
Martin C. Akogbéto Martin C. ,
SEZONLIN MICHEL ,
||Tropical Medicine and Health
||Background: Several studies have reported the strong resistance of Anopheles gambiae s.l. complex species to
pyrethroids. The voltage-dependent sodium channel (Vgsc) gene is the main target of pyrethroids and DDT. In Benin, the
frequency of the resistant allele (L1014F) of this gene varies along the north-south transect. Monitoring the evolution of
resistance is necessary to better appreciate the genetic structure of vector populations in localities subject to the intensive
use of chemicals associated with other control initiatives. The purpose of this study was to map the distribution of
pyrethroid insecticide resistance alleles of the Kdr gene in malaria vectors in different regions and ecological facies in
order to identify the evolutionary forces that might be the basis of anopheline population dynamics.
Methods: The characterization of Anopheles gambiae s.l. populations and resistance mechanisms were performed using
adult mosquitoes obtained from larvae collected in the four agroecological zones in southern Benin. Genomic DNA
extraction was performed on whole mosquitoes.
The extracted genomic DNA from them were used for the molecular identification of species in Anopheles gambiae s.l.
complex and the identification of genotypes related to pyrethroid resistance as the Kdr gene amino acid position 1014
in sodium channel. Molecular speciation and genotyping of Kdr resistant alleles (1014) were done using PCR.
Genepop software version 4.2 was used to calculate allelic and genotypic frequencies in each agroecological zone. The
p value of the allelic frequency was determined using the binomial test function in R version 3.3.3. The Hardy-Weinberg
equilibrium was checked for each population with Genetics software version 22.214.171.124. The observed heterozygosity and
the expected heterozygosity as well as the fixation index and genetic differentiation index within and between
populations were calculated using Genepop software version 4.2.
Results: During the study period, Anopheles coluzzii was the major species in all agroecological zones while Anopheles
gambiae was scarcely represented. Regardless of the species, resistant homozygote individuals (L1014F/L1014F) were
dominant in all agroecological zones, showing a strong selection of the resistant allele (L1014F). All populations
showed a deficit of heterozygosity. No genetic differentiation was observed between the different populations of the
two species. For Anopheles coluzzii, there was a small differentiation among the populations of the central cotton and
bar-lands zones. The genetic differentiation was modest among the population of the fisheries zone (Fst = 0.1295). The
genetic differentiation was very high in the population of Anopheles gambiae of the bar-lands zone (Fst = 0.2408).
Conclusion: This study revealed that the use of insecticides in Benin for years has altered the genetic structure of Anopheles
gambiae s.s. populations in all agroecological zones of southern Benin. It would be desirable to orientate vector control efforts
towards the use of insecticides other than pyrethroids and DDT or combinations of insecticides with different modes of action.
||Anopheles gambiae s.l., Genetic structure, Malaria, Resistance, Benin
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