BACKGROUND The yellow fever mosquito Aedes aegypti is the major vector of dengue, yellow fever, Zika, and Chikungunya viruses. Worldwide vector control is largely based on insecticide treatments but, unfortunately, vector control programs are facing operational challenges due to mosquitoes becoming resistant to commonly used insecticides. In Southeast Asia, resistance of Ae. aegypti to chemical insecticides has been documented in several countries but no data regarding insecticide resistance has been reported in Laos. To fill this gap, we assessed the insecticide resistance of 11 Ae. aegypti populations to larvicides and adulticides used in public health operations in the country. We also investigated the underlying molecular mechanisms associated with resistance, including target site mutations and detoxification enzymes putatively involved in metabolic resistance. METHODS AND RESULTS Bioassays on adults and larvae collected in five provinces revealed various levels of resistance to organophosphates (malathion and temephos), organochlorine (DDT) and pyrethroids (permethrin and deltamethrin). Synergist bioassays showed a significant increased susceptibility of mosquitoes to insecticides after exposure to detoxification enzyme inhibitors. Biochemical assays confirmed these results by showing significant elevated activities of cytochrome P450 monooxygenases (P450), glutathione S-transferases (GST) and carboxylesterases (CCE) in adults. Two kdr mutations, V1016G and F1534C, were detected by qPCR at low and high frequency, respectively, in all populations tested. A significant negative association between the two kdr mutations was detected. No significant association between kdr mutations frequency (for both 1534C and 1016G) and survival rate to DDT or permethrin (P > 0.05) was detected. Gene Copy Number Variations (CNV) were detected for particular detoxification enzymes. At the population level, the presence of CNV affecting the carboxylesterase CCEAE3A and the two cytochrome P450 CYP6BB2 and CYP6P12 were significantly correlated to insecticide resistance. CONCLUSIONS These results suggest that both kdr mutations and metabolic resistance mechanisms are present in Laos but their impact on phenotypic resistance may differ in proportion at the population or individual level. Molecular analyses suggest that CNV affecting CCEAE3A previously associated with temephos resistance is also associated with malathion resistance while CNV affecting CYP6BB2 and CYP6P12 are associated with pyrethroid and possibly DDT resistance. The presence of high levels of insecticide resistance in the main arbovirus vector in Laos is worrying and may have important implications for dengue vector control in the country.

中文翻译：

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老挝虫媒载体埃及伊蚊的分布及其对杀虫剂的抗药性及其对媒介控制的意义。

背景技术黄热蚊埃及伊蚊是登革热，黄热病，寨卡病毒和基孔肯雅病毒的主要载体。世界范围内的媒介控制主要是基于杀虫剂的处理，但是不幸的是，由于蚊子对常用杀虫剂产生了抵抗力，因此媒介控制计划面临着操作上的挑战。在东南亚，抗性强盛。在一些国家，埃及已对化学杀虫剂进行了埃及化，但老挝尚无关于杀虫剂抗药性的数据报道。为了填补这一空白，我们评估了11 Ae的杀虫剂抗性。埃及人口中在该国公共卫生活动中使用的杀幼虫剂和杀成虫剂。我们还研究了与抗性相关的潜在分子机制，包括可能与代谢抗性有关的靶位点突变和解毒酶。方法和结果在五个省份对成年和幼虫进行的生物测定表明，它们对有机磷酸盐（马拉硫磷和temephos），有机氯（DDT）和拟除虫菊酯（苄氯菊酯和溴氰菊酯）具有不同程度的抗药性。协同增效生物测定法显示，暴露于解毒酶抑制剂后，蚊子对杀虫剂的敏感性大大提高。生化分析通过显示成人中细胞色素P450单加氧酶（P450），谷胱甘肽S-转移酶（GST）和羧酸酯酶（CCE）的活性显着提高，证实了这些结果。通过qPCR在所有测试人群中分别以低频和高频检测到两个kdr突变，分别为V1016G和F1534C。在两个kdr突变之间检测到显着的负相关。在kdr突变频率（对于1534C和1016G而言）与DDT或氯菊酯的存活率之间没有显着相关性（P> 0.05）。检测了特定排毒酶的基因拷贝数变异（CNV）。在种群水平上，CNV的存在会影响羧酸酯酶CCEAE3A和两种细胞色素P450 CYP6BB2和CYP6P12的存在与杀虫剂抗性显着相关。结论这些结果表明，老挝存在kdr突变和代谢抗性机制，但它们对表型抗性的影响在人群或个体水平上可能有所不同。分子分析表明，影响CCEAE3A的CNV与以前的抗季戊酰胺耐药性也与马拉硫磷相关，而影响CYP6BB2和CYP6P12的CNV与拟除虫菊酯和可能对DDT的耐药性有关。老挝主要虫媒病毒载体中高水平的杀虫剂抗药性令人担忧，并可能对该国的登革热媒介控制产生重要影响。