Oliver Shüné V, Brooke Basil D
Centre for Opportunistic, Tropical and Hospital Infections, National Institute for Communicable Diseases/NHLS, Sandringham, Johannesburg, South Africa.
Parasit Vectors. 2014 Aug 23;7:390. doi: 10.1186/1756-3305-7-390.
Anopheles arabiensis is a major malaria vector in Africa. Adult females are likely to imbibe multiple blood meals during their lifetime. This results in regular exposure to potential toxins and blood-meal induced oxidative stress. Defence responses to these stressors may affect other factors of epidemiological significance, such as insecticide resistance and longevity. The aims of this study were to examine the effect of multiple blood-feeding on insecticide tolerance/resistance with increasing age, to assess the underlying biochemical mechanisms for the responses recorded, and to assess the effect of multiple blood-feeding on the life histories of adult females drawn from insecticide resistant and susceptible laboratory reared An. arabiensis.
Laboratory reared An. arabiensis females from an insecticide resistant and an insecticide susceptible colony were offered either a single blood meal or multiple blood meals at 3-day intervals. Their tolerance or resistance to insecticide was then monitored by WHO bioassay four hours post blood-feeding. The biochemical basis of the phenotypic response was assessed by examining the effect of blood on detoxification enzyme activity and the effect of blood-meals on detoxification enzyme activity in ageing mosquitoes.
Control cohorts that were not offered any blood meals showed steadily decreasing levels of insecticide tolerance/resistance with age, whereas a single blood meal significantly increased tolerance/resistance primarily at the age of three days. The expression of resistance/tolerance in those cohorts fed multiple blood meals generally showed the least variation with age. These results were consistent following exposure to DDT and pyrethroids but not to malathion. Multiple blood-meals also maintained the DDT and permethrin resistant phenotype, even after treatment females had stopped taking blood-meals. Biochemical analysis suggests that this phenotypic effect in resistant females may be mediated by the maintenance of increased glutathione s-transferase activity as a consequence of multiple blood-feeding. Multiple blood-feeding increased the longevity of insecticide resistant females regardless of their mating status, but only increased the longevity of unmated susceptible females.
These data suggest that multiple blood-feeding confers a competitive advantage to insecticide resistant females by increased longevity and maintenance of the expression of resistance with age.
阿拉伯按蚊是非洲主要的疟疾传播媒介。成年雌性按蚊在其一生中可能会多次吸食血液。这导致它们经常暴露于潜在毒素和血餐诱导的氧化应激中。对这些应激源的防御反应可能会影响其他具有流行病学意义的因素，如杀虫剂抗性和寿命。本研究的目的是研究多次吸血对随着年龄增长的杀虫剂耐受性/抗性的影响，评估所记录反应的潜在生化机制，并评估多次吸血对来自抗杀虫剂和敏感的实验室饲养阿拉伯按蚊成年雌性寿命的影响。
从抗杀虫剂和敏感群体中饲养的实验室饲养的阿拉伯按蚊雌性，每隔3天提供一次单血餐或多次血餐。然后在吸血后4小时通过世卫组织生物测定法监测它们对杀虫剂的耐受性或抗性。通过检查血液对解毒酶活性的影响以及血餐对衰老蚊子解毒酶活性的影响，评估表型反应的生化基础。
未提供任何血餐的对照队列显示，随着年龄的增长，杀虫剂耐受性/抗性水平稳步下降，而单血餐主要在三天龄时显著提高了耐受性/抗性。那些多次吸血的队列中抗性/耐受性的表达通常随年龄变化最小。接触滴滴涕和拟除虫菊酯后这些结果是一致的，但接触马拉硫磷后并非如此。即使在处理后的雌性停止吸血后，多次血餐也能维持对滴滴涕和氯菊酯的抗性表型。生化分析表明，抗性雌性中的这种表型效应可能是由于多次吸血导致谷胱甘肽S-转移酶活性增加而介导的。无论交配状态如何，多次吸血都增加了抗杀虫剂雌性的寿命，但仅增加了未交配敏感雌性的寿命。
这些数据表明，多次吸血通过延长寿命和维持随着年龄增长的抗性表达，赋予抗杀虫剂雌性竞争优势。
