ArticleMalaria journal2025
Characterization of insecticide resistance mechanisms in the Anopheles gambiae population of Sierra Leone.
Article in Malaria journal, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 5 papers, 1 of them a synthesis that pooled it.
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5 citing papers in PubMed, 1 synthesis or guideline pooled it.
- Performance assessment of Bayesian meta-analytic predictive model on kdr mutation in insecticide-resistant malarial vectors in sub-Saharan Africa.Malaria journal · 2025Pooled it
- Integrating routinely collected mosquito vector and human behavioral data for malaria prevention: A case example in central region Malawi.Malaria journal · 2026Article
- Optimizing insecticide deployment strategies to delay quantitative resistance in mosquito populations.Journal of mathematical biology · 2026Article
- An investigation of malaria vector populations in Turkana, Kenya to understand the potential impact of insecticide-treated nets.npj entomology · 2026Article
- What is the potential impact of insecticide treated nets in a semi-arid region of northern Kenya? An investigation of vector populations prior to ITN roll-out in Turkana, Kenya.Research square · 2025Article
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Abstract
backgroundInformation on the status of insecticide resistance in malaria vectors is critical for implementing effective malaria vector control. The Sierra Leone National Malaria Control Programme, in collaboration with the PMI VectorLink project, assessed the resistance status to insecticides commonly used in public health, and associated resistance mechanisms in Anopheles gambiae, the main vector of malaria in Sierra Leone.
methodsThe susceptibility of An. gambiae against pyrethroids with and without piperonyl butoxide (PBO), chlorfenapyr, clothianidin, bendiocarb and pirimiphos-methyl was evaluated in four districts of Sierra Leone in 2018 and 2019 using WHO and CDC bottle bioassay protocols. A subset of samples that were exposed to the insecticides were screened for molecular markers of insecticide resistance, knock-down resistance (kdr) L1014F, 1014S and N1575Y, and (ace-1-G119S).
resultsAnopheles gambiae from all sites were resistant to the diagnostic doses of three pyrethroids: deltamethrin, permethrin and alpha-cypermethrin. Intensity of resistance to all three pyrethroids was high, with less than 95% mortality at 10X concentration. However, pre-exposure of An. gambiae to PBO increased overall mortality by 41.6%, 50.0% and 44.0% for deltamethrin, permethrin and alpha-cypermethrin, respectively. The vector was susceptible to chlorfenapyr, clothianidin and pirimiphos-methyl, while bendiocarb showed possible resistance. The frequency of kdr alleles was 98.2% for L1014F, 2.1% for 1014S and 8.9% for N1575Y, while the frequency of the Ace-1 G119S allele was 13.6%. Significant deviation from the Hardy-Weinberg equilibrium and deficiency of heterozygotes was detected only at the G119S locus of An. gambiae (p < 0.0001). Of the 191 An. gambiae sensu lato that were molecularly identified to the species level, 81.7% were An. gambiae sensu stricto (95% CI 75.3-86.7), followed by Anopheles coluzzii (17.8%, 95% CI (12.8-24.1) with one hybrid of An. gambiae/An. coluzzii 0.5%, 95% CI (0.03-3.3).
conclusionMalaria vectors were highly resistant to pyrethroids but exposure to PBO partially restored susceptibility in An. gambiae s.l. in Sierra Leone. Malaria vectors were susceptible to chlorfenapyr, clothianidin and pirimiphos-methyl with possible resistance to bendiocarb. These data informed the selection and distribution of ITN PBO in Sierra Leone's mass campaigns in 2020 and selection of clothianidin for indoor residual spraying in 2021.
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