Abstract
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.
Highlights
Information on insecticide resistance and the mechanisms driving it in the major malaria vectors is grossly lacking in Niger Republic, hindering control efforts
From the 316 female An. coluzzii transferred into 1.5 ml only 147 (46.5%) laid eggs successfully, due to high mortality experienced while travelling to insectary at Kano, Nigeria
The finding of P. falciparum sporozoite rate of ~ 13% in this study suggests that this vector is sustaining a high level of malaria transmission despite ongoing control efforts
Summary
Information on insecticide resistance and the mechanisms driving it in the major malaria vectors is grossly lacking in Niger Republic, hindering control efforts. Niger Republic, with a high transmission and increased case incidence (2010–2016), is among countries with the highest per capita rate of malaria fatalities globally [6]. It alone accounts for ~ 4% of malaria burden in the world [4]. Generating reliable data on indigenous Sahelian Anopheles species, their contribution to malaria transmission and monitoring insecticide resistance status over time and space [4], is a pre-requisite for implementation of evidence-based control measures in this dry region
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