Department of Biosciences, Faculty of Science and Engineering, Swansea University, Swansea, UK.
Department of Biology, Faculty of Science, University of Tabuk, Tabuk, Kingdom of Saudi Arabia.
J Med Entomol. 2022 Sep 14;59(5):1732-1740. doi: 10.1093/jme/tjac110.
Aedes aegypti mosquitoes are capable of vectoring a wide range of diseases including dengue, yellow fever, and Zika viruses, with approximately half of the worlds' population at risk from such diseases. Development of combined predator-parasite treatments for the control of larvae consistently demonstrates increased efficacy over single-agent treatments, however, the mechanism behind the interaction remains unknown. Treatments using the natural predator Toxorhynchites brevipalpis and the entomopathogenic fungus Metarhizium brunneum were applied in the laboratory against Ae. aegypti larvae as both individual and combined treatments to determine the levels of interaction between control strategies. Parallel experiments involved the removal of larvae from test arenas at set intervals during the course of the trial to record whole body caspase and phenoloxidase activities. This was measured via luminometric assay to measure larval stress factors underlying the interactions. Combined Metarhizium and Toxorhynchites treatments were seen to drastically reduce lethal times as compared to individual treatments. This was accompanied by increased phenoloxidase and caspase activities in combination treatments after 18 h (p < 0.001). The sharp increases in caspase and phenoloxidase activities suggest that combined treatments act to increase stress factor responses in the larvae that result in rapid mortality above that of either control agent individually. This work concludes that the underlying mechanism for increased lethality in combined parasite-predator treatments may be related to additive stress factors induced within the target host larvae.
埃及伊蚊能够传播多种疾病，包括登革热、黄热病和寨卡病毒，全球约有一半的人口面临这些疾病的风险。开发针对幼虫的联合捕食者-寄生虫治疗方法可显著提高单一药物治疗的效果，然而，这种相互作用的机制尚不清楚。实验室中使用自然捕食者 Toxorhynchites brevipalpis 和昆虫病原真菌 Metarhizium brunneum 作为单独和联合处理方法来控制埃及伊蚊幼虫，以确定控制策略之间的相互作用水平。平行实验涉及在试验过程中每隔一段时间从测试场中取出幼虫，以记录整个身体 Caspase 和酚氧化酶的活性。通过发光测定法来测量潜在的相互作用的幼虫应激因子。与单独处理相比，联合使用 Metarhizium 和 Toxorhynchites 处理可大大缩短致死时间。这伴随着组合处理后 18 小时内酚氧化酶和 Caspase 活性的增加（p < 0.001）。Caspase 和酚氧化酶活性的急剧增加表明，联合处理会增加幼虫中的应激因子反应，导致死亡率迅速上升，超过单独使用任何一种对照剂。这项工作得出的结论是，联合寄生虫-捕食者处理中致死率增加的潜在机制可能与目标宿主幼虫内诱导的附加应激因子有关。
