Centre de Recherche Entomologique de Cotonou, Cotonou, Bénin.
Faculté des Sciences et Techniques-Université d'Abomey-Calavi, Abomey Calavi, Bénin.
Parasit Vectors. 2024 Mar 7;17(1):115. doi: 10.1186/s13071-024-06206-8.
Indoor residual spraying (IRS) was first implemented in the Atacora department, Benin from 2011 to 2012 using bendiocarb (carbamate) followed by annual spraying with pirimiphos-methyl (organophosphate) from 2013 to 2018. Before and after IRS implementation in Atacora, standard pyrethroid insecticide-treated bed nets were the main method of vector control in the area. This study investigated the knockdown resistance (kdr) gene (L1014F) and the acetylcholinesterase (ace-1) gene (G119S), before and during IRS implementation, and 4-years after IRS withdrawal from Atacora. This was done to assess how changes in insecticide pressure from indoor residual spraying may have altered the genotypic resistance profile of Anopheles gambiae s.l.
Identification of sibling species of An. gambiae s.l. and detection of the L1014F mutation in the kdr gene and G119S mutation in ace-1 genes was done using molecular analysis. Allelic and genotypic frequencies were calculated and compared with each other before and during IRS implementation and 4 years after IRS withdrawal. The Hardy-Weinberg equilibrium and genetic differentiation within and between populations were assessed.
Prevalence of the L1014F mutation in all geographic An. gambiae s.l. (An. gambiae s.s., Anopheles. coluzzii, Anopheles. arabiensis, and hybrids of "An. gambiae s.s. and An. coluzzii") populations increased from 69% before IRS to 87% and 90% during and after IRS. The G119S allele frequency during IRS (20%) was significantly higher than before IRS implementation (2%). Four years after IRS withdrawal, allele frequencies returned to similar levels as before IRS (3%). Four years after IRS withdrawal, the populations showed excess heterozygosity at the ace-1 gene and deficit heterozygosity at the kdr gene, whereas both genes had excess heterozygosity before and during IRS (F < 0). No genetic differentiation was observed within the populations.
This study shows that the withdrawal of IRS with bendiocarb and pirimiphos-methyl may have slowed down the selection of individual mosquitoes with ace-1 resistance alleles in contrast to populations of An. gambiae s.l. with the L1014F resistance allele of the kdr gene. This may suggest that withdrawing the use of carbamates or organophosphates from IRS or rotating alternative insecticides with different modes of action may slow the development of ace-1 insecticide-resistance mutations. The increase in the prevalence of the L1014F mutation of the kdr gene in the population, despite the cessation of IRS, could be explained by the growing use of pyrethroids and DDT in agriculture and for other domestic use. More observational studies in countries where carbamates or organophosphates are still being used as public health insecticides may provide additional insights into these associations.
2011 年至 2012 年，贝宁阿塔科拉省首次使用苯氧威（氨基甲酸酯类）实施室内滞留喷洒（IRS），随后从 2013 年至 2018 年每年使用吡虫磷（有机磷类）进行喷洒。在阿塔科拉实施 IRS 前后，标准的拟除虫菊酯类杀虫剂处理过的蚊帐是该地区主要的病媒控制方法。本研究在 IRS 实施前后以及 IRS 停止 4 年后，调查了击倒抗性（kdr）基因（L1014F）和乙酰胆碱酯酶（ace-1）基因（G119S）。这是为了评估室内滞留喷洒中杀虫剂压力的变化如何改变冈比亚按蚊复合体的基因型抗性特征。
使用分子分析鉴定冈比亚按蚊复合体的姐妹种，并检测 kdr 基因中的 L1014F 突变和 ace-1 基因中的 G119S 突变。计算等位基因和基因型频率，并在 IRS 实施前后以及 IRS 停止 4 年后进行比较。评估了 Hardy-Weinberg 平衡和种群内和种群间的遗传分化。
所有地理种群（冈比亚按蚊复合体、冈比亚按蚊、阿拉伯按蚊和“冈比亚按蚊和冈比亚按蚊”的杂种）中 L1014F 突变的流行率从 IRS 前的 69%增加到 IRS 期间的 87%和 IRS 后的 90%。IRS 期间 ace-1 基因的 G119S 等位基因频率（20%）明显高于 IRS 实施前（2%）。IRS 停止 4 年后，等位基因频率恢复到 IRS 前的相似水平（3%）。IRS 停止 4 年后，种群在 ace-1 基因中表现出杂合过剩，而在 kdr 基因中表现出杂合不足，而在 IRS 前后，这两个基因都表现出杂合过剩（F < 0）。种群内没有观察到遗传分化。
本研究表明，停止使用苯氧威和吡虫磷进行 IRS 可能会减缓携带 ace-1 抗性等位基因的个体蚊子的选择，而携带 kdr 基因 L1014F 抗性等位基因的冈比亚按蚊复合体种群则不然。这可能表明，从 IRS 中停止使用氨基甲酸酯类或有机磷类杀虫剂，或轮换具有不同作用模式的替代杀虫剂，可能会减缓 ace-1 杀虫剂抗性突变的发展。尽管 IRS 已经停止，但 kdr 基因 L1014F 突变的流行率在种群中增加，这可能是由于农业和其他家庭用途中越来越多地使用拟除虫菊酯类和滴滴涕类杀虫剂所致。在仍在将氨基甲酸酯类或有机磷类作为公共卫生杀虫剂使用的国家进行更多的观察性研究，可能会为这些关联提供更多的见解。
