Dataset Information

Tracing the origin of the early wet-season Anopheles coluzzii in the Sahel.

ABSTRACT: In arid environments, the source of the malaria mosquito populations that re-establish soon after first rains remains a puzzle and alternative explanations have been proposed. Using genetic data, we evaluated whether the early rainy season (RS) population of Anopheles coluzzii is descended from the preceding late RS generation at the same locality, consistent with dry season (DS) dormancy (aestivation), or from migrants from distant locations. Distinct predictions derived from these two hypotheses were assessed, based on variation in 738 SNPs in eleven A. coluzzii samples, including seven samples spanning 2 years in a Sahelian village. As predicted by the "local origin under aestivation hypothesis," temporal samples from the late RS and those collected after the first rain of the following RS were clustered together, while larger genetic distances were found among samples spanning the RS. Likewise, multilocus genotype composition of samples from the end of the RS was similar across samples until the following RS, unlike samples that spanned the RS. Consistent with reproductive arrest during the DS, no genetic drift was detected between samples taken over that period, despite encompassing extreme population minima, whereas it was detected between samples spanning the RS. Accordingly, the variance in allele frequency increased with time over the RS, but not over the DS. However, not all the results agreed with aestivation. Large genetic distances separated samples taken a year apart, and during the first year, within-sample genetic diversity declined and increased back during the late RS, suggesting a bottleneck followed by migration. The decline of genetic diversity followed by a mass distribution of insecticide-treated nets was accompanied by a reduced mosquito density and a rise in the mutation conferring resistance to pyrethroids, indicating a bottleneck due to insecticidal selection. Overall, our results support aestivation in A. coluzzii during the DS that is accompanied by long-distance migration in the late RS.

SUBMITTER: Lehmann T

PROVIDER: S-EPMC5511357 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Tracing the origin of the early wet-season <i>Anopheles coluzzii</i> in the Sahel.

Lehmann Tovi T Weetman David D Huestis Diana L DL Yaro Alpha S AS Kassogue Yaya Y Diallo Moussa M Donnelly Martin J MJ Dao Adama A

Evolutionary applications 20170526 7

In arid environments, the source of the malaria mosquito populations that re-establish soon after first rains remains a puzzle and alternative explanations have been proposed. Using genetic data, we evaluated whether the early rainy season (RS) population of <i>Anopheles coluzzii</i> is descended from the preceding late RS generation at the same locality, consistent with dry season (DS) dormancy (aestivation), or from migrants from distant locations. Distinct predictions derived from these two h ...[more]

PMID: 28717390

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Project description:BackgroundInformation on insecticide resistance and the mechanisms driving it in the major malaria vectors is grossly lacking in Niger Republic, thus hindering control efforts. To facilitate evidence-based malaria control, the role of Anopheles coluzzii population from southern Niger, in malaria transmission, its insecticides resistance profile and the molecular mechanisms driving the resistance were characterized.MethodsBlood fed female Anopheles gambiae sensu lato resting indoor were collected at Tessaoua, Niger. Source of blood was established using PCR and infection with Plasmodium determined using TaqMan assay. Resistance profile was established with the major public health insecticides, and resistance intensity determined with deltamethrin. Synergist assays were conducted with piperonyl butoxide and diethyl maleate. Presence of L1014F and L1014S knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC) was investigated using TaqMan genotyping, and strength of selection pressure acting on the Anopheles populations determined by assessing the genetic diversity of a fragment spanning exon-20 of the VGSC from alive and dead females.ResultsHigh human blood index (96%) and high Plasmodium falciparum infection (~ 13%) was observed in the An. coluzzii population. Also, a single mosquito was found infected with Plasmodium vivax. High pyrethroid and organochloride resistance was observed with mortalities of less than 20% for deltamethrin, permethrin, α-cypermethrin, and DDT. A high LD50 (156.65 min) was obtained for deltamethrin, with a resistance ratio of ~ 47.18 compared to the susceptible Ngoussou colony. Moderate carbamate resistance was observed, and a full susceptibility to organophosphates recorded. Synergist bioassays with piperonyl butoxide and diethyl maleate significantly recovered deltamethrin and DDT susceptibility, respectively implicating CYP450 s (mortality = 82%, χ2 = 84.51, p < 0.0001) and glutathione S-transferases (mortality = 58%, χ2 = 33.96, p < 0.001) in resistance. A high frequency of 1014F kdr mutation (82%) was established, with significant difference in genotype distribution associated with permethrin resistance [odds ratio = 7.71 (95% CI 2.43-14.53, χ2 = 13.67, p = 0.001]. Sequencing of intron-1 of the voltage-gated sodium channel (VGSC) revealed a low genetic diversity.ConclusionHigh pyrethroid resistance highlight the challenges to the effectiveness of the pyrethroids-based ITNs and indoor residual spraying (IRS) against An. coluzzii in Niger. The pyrethroids-synergists LLINs and organophosphate-based IRS maybe the alternatives for malaria control in southern Niger.

Dataset Information

Tracing the origin of the early wet-season Anopheles coluzzii in the Sahel.

Publications

Tracing the origin of the early wet-season <i>Anopheles coluzzii</i> in the Sahel.

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