Kudom Andreas A, Mensah Ben A, Froeschl Guenter, Boakye Daniel, Rinder Heinz
Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Munich, Germany.
Department of Entomology and Wildlife, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana.
Parasit Vectors. 2015 Jan 8;8:8. doi: 10.1186/s13071-014-0621-4.
Besides its role as a pathogen vector, Culex species also indirectly promotes the transmission of malaria if the use of bed nets or indoor residual spraying is discontinued due to a lack of insecticide efficacy against it. A recent survey revealed widespread occurrence of pyrethroid resistance among urban populations of this mosquito in Ghana. In order to plan and implement insecticide-based resistance management strategies, this study was carried out to assess resistance status of Culex species to organophosphate and carbamate in urban areas in Ghana and the possible mechanisms involved as well as environmental factors associated with its distribution.
Mosquito larvae were sampled from various land use and ecological settings and in different seasons. In adults, susceptibility to organophosphates (fenitrothion, malathion) and carbamates (propoxur, bendiocarb) were determined. Mixed function oxidase (MFO) and α- and β-esterase assays, as well as a PCR diagnostic assay to determine ace1 mutation were performed in individual mosquitoes.
Culex quinquefasciatus as well as C. decens and other unidentified Culex species were found breeding in polluted water bodies in the study sites. Across all sites and seasons, carbamate induced mortality was 94.1% ± 15.4 whereas mortality caused by organophosphate was 99.5% ± 2.2. In addition, ace1 mutation and high levels of esterases were detected in some of the mosquito populations. There was a strong correlation between susceptibility status of the mosquitoes and the level of absorbance of β-esterase (Pearson r=- 0.841, p=0.004).
The study found low prevalence of resistance to carbamate and organophosphate insecticides among Culex species from Ghana. However, there were populations with ace1 mutations and high levels of esterases, which can confer high resistance to these classes of insecticides. Thus, it is important to monitor activities or behaviour that has the potential to select for carbamate and organophosphate resistance populations.
库蚊属除了作为病原体载体外，如果由于对其缺乏杀虫剂效力而停止使用蚊帐或室内滞留喷洒，还会间接促进疟疾传播。最近一项调查显示，加纳该蚊种城市种群中拟除虫菊酯抗性普遍存在。为了规划和实施基于杀虫剂的抗性管理策略，开展了本研究，以评估加纳城市地区库蚊属对有机磷和氨基甲酸酯的抗性状况、可能涉及的机制以及与其分布相关的环境因素。
在不同土地利用和生态环境以及不同季节采集蚊虫幼虫。测定成虫对有机磷（杀螟硫磷、马拉硫磷）和氨基甲酸酯（残杀威、仲丁威）的敏感性。对单个蚊虫进行混合功能氧化酶（MFO）、α-和β-酯酶测定，以及用于确定ace1突变的聚合酶链反应诊断测定。
在研究地点的污染水体中发现致倦库蚊、骚扰库蚊和其他未鉴定的库蚊种类在繁殖。在所有地点和季节，氨基甲酸酯引起的死亡率为94.1%±15.4，而有机磷引起的死亡率为99.5%±2.2。此外，在一些蚊虫种群中检测到ace1突变和高水平的酯酶。蚊虫的敏感性状况与β-酯酶的吸光度水平之间存在很强的相关性（皮尔逊r=-0.841，p=0.004）。
该研究发现加纳库蚊属对氨基甲酸酯和有机磷杀虫剂的抗性流行率较低。然而，存在ace1突变和高水平酯酶的种群，这可能赋予对这些类别的杀虫剂的高抗性。因此，监测有可能选择出对氨基甲酸酯和有机磷有抗性的种群的活动或行为非常重要。
