Oliver Shüné V, Brooke Basil D
Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa.
Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
PLoS One. 2018 Feb 6;13(2):e0192551. doi: 10.1371/journal.pone.0192551. eCollection 2018.
Metal exposure is one of the commonest anthropogenic pollutants mosquito larvae are exposed to, both in agricultural and urban settings. As members of the Anopheles gambiae complex, which contains several major malaria vector species including An. arabiensis, are increasingly adapting to polluted environments, this study examined the effects of larval metal exposure on various life history traits of epidemiological importance. Two laboratory strains of An. arabiensis, SENN (insecticide susceptible) and SENN DDT (insecticide resistant), were reared in maximum acceptable toxicity concentrations, (MATC-the highest legally accepted concentration) of cadmium chloride, lead nitrate and copper nitrate. Following these exposures, time to pupation, adult size and longevity were determined. Larvae reared in double the MATC were assessed for changes in malathion and deltamethrin tolerance, measured by lethal time bottle bioassay, as well as changes in detoxification enzyme activity. As defence against oxidative stress has previously been demonstrated to affect the expression of insecticide resistance, catalase, glutathione peroxidase and superoxide dismutase activity was assessed. The relative metal toxicity to metal naïve larvae was also assessed. SENN DDT larvae were more tolerant of metal pollution than SENN larvae. Pupation in SENN larvae was significantly reduced by metal exposure, while adult longevity was not affected. SENN DDT showed decreased adult size after larval metal exposure. Adult insecticide tolerance was increased after larval metal exposure, and this effect appeared to be mediated by increased β-esterase, cytochrome P450 and superoxide dismutase activity. These data suggest an enzyme-mediated positive link between tolerance to metal pollutants and insecticide resistance in adult mosquitoes. Furthermore, exposure of larvae to metal pollutants may have operational consequences under an insecticide-based vector control scenario by increasing the expression of insecticide resistance in adults.
金属暴露是农业和城市环境中蚊子幼虫接触到的最常见的人为污染物之一。冈比亚按蚊复合体的成员，包括阿拉伯按蚊等几种主要的疟疾传播媒介物种，正越来越适应污染环境，本研究调查了幼虫期金属暴露对各种具有流行病学重要性的生活史特征的影响。使用阿拉伯按蚊的两个实验室品系，即SENN（对杀虫剂敏感）和SENN DDT（对杀虫剂耐药），在氯化镉、硝酸铅和硝酸铜的最大可接受毒性浓度（MATC，即法律上可接受的最高浓度）下进行饲养。经过这些暴露处理后，测定化蛹时间、成虫大小和寿命。将饲养在两倍MATC浓度下的幼虫进行马拉硫磷和溴氰菊酯耐受性变化的评估，通过致死时间瓶生物测定法进行测量，同时评估解毒酶活性的变化。由于先前已证明抗氧化应激防御会影响杀虫剂抗性的表达，因此评估了过氧化氢酶、谷胱甘肽过氧化物酶和超氧化物歧化酶的活性。还评估了金属对未接触过金属的幼虫的相对毒性。SENN DDT幼虫比SENN幼虫对金属污染更具耐受性。金属暴露显著降低了SENN幼虫的化蛹率，而成虫寿命未受影响。SENN DDT在幼虫期金属暴露后成虫大小减小。幼虫期金属暴露后成虫对杀虫剂的耐受性增加，这种效应似乎是由β-酯酶、细胞色素P450和超氧化物歧化酶活性增加介导的。这些数据表明成年蚊子对金属污染物的耐受性与杀虫剂抗性之间存在酶介导的正相关联系。此外，在基于杀虫剂的病媒控制方案下，幼虫接触金属污染物可能会因增加成虫对杀虫剂抗性的表达而产生实际影响。
