Yadouléton Agnes, Badirou Kefilath, Agbanrin Ramziath, Jöst Hanna, Attolou Roseline, Srinivasan Ramasamy, Padonou Gil, Akogbéto Martin
Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, République du Bénin.
Ecole Normale Supérieure de Natitingou-Université de Parakou, Parakou, Benin.
Parasit Vectors. 2015 Jan 13;8:17. doi: 10.1186/s13071-015-0638-3.
Culex quinquefasciatus, an arboviral and filarial vector, is present year round in several cities of the Republic of Benin. There is more information on the resistance status to malaria vectors compared to Culicines. It is therefore unfortunate that the international focus is on Anopheles control and not so much done against Cx. quinquefasciatus, a rather more resilient mosquito to many insecticides that deserves attention. The present study aims to assess the resistance status of Cx. quinquefasciatus to carbamates, pyrethroids and organochlorine and discuss the implications for vector control in four contrasting localities of the country.
Four contrasting localities of the country were selected for mosquito collection during the dry season based on their variation in agricultural production, use of insecticides and/or ecological settings. Bioassay were performed on adults collected from the field to assess the susceptibility of Cx. quinquefasciatus to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. Molecular assays were carried out to detect the presence of knock down resistance (kdr) and acetylcholinesterase (ace. 1) mutations in surviving specimens using PCR techniques.
WHO diagnostic tests showed high frequency of resistance in Cx. quinquefasciatus to permethrin (ranging from 4 to 24% mortality), deltamethrin (24 to 48%), DDT (4 to 12%) and bendiocarb (60 to 76%) in the four selected areas. This was consistent with the presence of target site insensitivity due to kdr and ace.1 mutations, which were significantly higher in areas where farmers used insecticides for pests control than in areas where no insecticides were used (p < 0.05.).
These findings showed that wild populations of Cx. quinquefasciatus have developed resistance against pyrethroids, organochlorine and carbamate. This situation of resistance may seriously jeopardize the efficacy of Insecticide Residual Spray (IRS) and Long-Lasting Insecticide nets (LLINs) on which, most African countries including Benin, rely to reduce malaria transmission.
致倦库蚊是一种虫媒病毒和丝虫病的传播媒介，在贝宁共和国的几个城市全年都有出现。与库蚊亚科相比，关于疟蚊抗药性状况的信息更多。因此，不幸的是，国际上的重点是按蚊控制，而针对致倦库蚊（一种对许多杀虫剂更具抵抗力且值得关注的蚊子）所做的工作却不多。本研究旨在评估致倦库蚊对氨基甲酸酯类、拟除虫菊酯类和有机氯的抗药性状况，并讨论其对该国四个不同地区病媒控制的影响。
根据农业生产、杀虫剂使用情况和/或生态环境的差异，在旱季选择该国四个不同地区进行蚊虫采集。按照世界卫生组织杀虫剂评价计划（WHOPES）的指导方针，对从野外采集的成虫进行生物测定，以评估致倦库蚊对杀虫剂浸渍纸（氯菊酯0.75%、溴氰菊酯0.05%、滴滴涕4%和残杀威0.1%）的敏感性。采用聚合酶链反应（PCR）技术进行分子检测，以检测存活标本中击倒抗性（kdr）和乙酰胆碱酯酶（ace.1）突变的存在情况。
世界卫生组织的诊断测试表明，在四个选定地区，致倦库蚊对氯菊酯（死亡率在4%至24%之间）、溴氰菊酯（24%至48%）、滴滴涕（4%至12%）和残杀威（60%至76%）的抗性频率很高。这与因kdr和ace.1突变导致的靶标位点不敏感的存在情况一致，在农民使用杀虫剂防治害虫的地区，这种情况明显高于未使用杀虫剂的地区（p < 0.05）。
这些研究结果表明，致倦库蚊的野生种群已对拟除虫菊酯类、有机氯和氨基甲酸酯类产生了抗性。这种抗药性情况可能会严重危及包括贝宁在内的大多数非洲国家所依赖的室内滞留喷洒（IRS）和长效驱虫蚊帐（LLINs）减少疟疾传播的效果。
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