Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303 Abidjan 01, Abidjan, Côte d'Ivoire.
Université Nangui Abrogoua, Abidjan, Côte d'Ivoire.
Parasit Vectors. 2023 Aug 9;16(1):270. doi: 10.1186/s13071-023-05876-0.
Insecticide-based malaria vector control is increasingly undermined due to the development of insecticide resistance in mosquitoes. Insecticide resistance may partially be related to the use of pesticides in agriculture, while the level and mechanisms of resistance might differ between agricultural practices. The current study aimed to assess whether phenotypic insecticide resistance and associated molecular resistance mechanisms in Anopheles gambiae sensu lato differ between agricultural practices.
We collected An. gambiae s.l. larvae in six sites with three different agricultural practices, including rice, vegetable and cocoa cultivation. We then exposed the emerging adult females to discriminating concentrations of bendiocarb (0.1%), deltamethrin (0.05%), DDT (4%) and malathion (5%) using the standard World Health Organization insecticide susceptibility test. To investigate underlying molecular mechanisms of resistance, we used multiplex TaqMan qPCR assays. We determined the frequency of target-site mutations, including Vgsc-L995F/S and Vgsc-N1570Y, and Ace1-G280S. In addition, we measured the expression levels of genes previously associated with insecticide resistance in An. gambiae s.l., including the cytochrome P450-dependent monooxygenases CYP4G16, CYP6M2, CYP6P1, CYP6P3, CYP6P4, CYP6Z1 and CYP9K1, and the glutathione S-transferase GSTe2.
The An. gambiae s.l. populations from all six agricultural sites were resistant to bendiocarb, deltamethrin and DDT, while the populations from the two vegetable cultivation sites were additionally resistant to malathion. Most tested mosquitoes carried at least one mutant Vgsc-L995F allele that is associated with pyrethroid and DDT resistance. In the cocoa cultivation sites, we observed the highest 995F frequencies (80-87%), including a majority of homozygous mutants and several in co-occurrence with the Vgsc-N1570Y mutation. We detected the Ace1 mutation most frequently in vegetable-growing sites (51-60%), at a moderate frequency in rice (20-22%) and rarely in cocoa-growing sites (3-4%). In contrast, CYP6M2, CYP6P3, CYP6P4, CYP6Z1 and CYP9K1, previously associated with metabolic insecticide resistance, showed the highest expression levels in the populations from rice-growing sites compared to the susceptible Kisumu reference strain.
In our study, we observed intriguing associations between the type of agricultural practices and certain insecticide resistance profiles in the malaria vector An. gambiae s.l. which might arise from the use of pesticides deployed for protecting crops.
由于蚊子对杀虫剂的抗药性不断增强，基于杀虫剂的疟疾媒介控制越来越受到影响。杀虫剂抗性可能部分与农业中农药的使用有关，而农业实践之间的抗性水平和机制可能不同。本研究旨在评估农业实践中是否存在按蚊属按蚊种间表型杀虫剂抗性和相关分子抗性机制的差异。
我们在 6 个地点收集了按蚊属按蚊种间的幼虫，这些地点有 3 种不同的农业实践，包括水稻、蔬菜和可可种植。然后，我们使用标准的世界卫生组织杀虫剂敏感性测试，用苯氧威（0.1%）、溴氰菊酯（0.05%）、滴滴涕（4%）和马拉硫磷（5%）对出现的成年雌性进行了区分浓度的暴露。为了研究潜在的分子抗性机制，我们使用了多重 TaqMan qPCR 检测。我们确定了靶位突变的频率，包括 Vgsc-L995F/S 和 Vgsc-N1570Y，以及 Ace1-G280S。此外，我们还测量了先前与按蚊属按蚊种间杀虫剂抗性相关的基因的表达水平，包括细胞色素 P450 依赖性单加氧酶 CYP4G16、CYP6M2、CYP6P1、CYP6P3、CYP6P4、CYP6Z1 和 CYP9K1，以及谷胱甘肽 S-转移酶 GSTe2。
来自所有 6 个农业地点的按蚊属按蚊种间种群对苯氧威、溴氰菊酯和滴滴涕均具有抗性，而来自两个蔬菜种植地点的种群对马拉硫磷也具有抗性。大多数经测试的蚊子至少携带一个与拟除虫菊酯和滴滴涕抗性相关的突变 Vgsc-L995F 等位基因。在可可种植地点，我们观察到最高的 995F 频率（80-87%），包括大多数纯合突变体和几个与 Vgsc-N1570Y 突变共存的突变体。我们在蔬菜种植地点最常检测到 Ace1 突变（51-60%），在水稻种植地点中等频率（20-22%），在可可种植地点很少（3-4%）。相比之下，先前与代谢性杀虫剂抗性相关的 CYP6M2、CYP6P3、CYP6P4、CYP6Z1 和 CYP9K1 在水稻种植地点的种群中的表达水平最高，与敏感的基苏木参考株相比。
在本研究中，我们观察到农业实践类型与疟疾媒介按蚊属按蚊种间某些杀虫剂抗性特征之间存在有趣的关联，这可能是由于用于保护作物的农药的使用而产生的。
