Time-to-response toxicity analysis as a method for drug susceptibility assessment in salmon lice.
Time-to-response toxicity analysis as a method for drug susceptibility assessment in salmon lice.
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DOI：
10.1016/j.aquaculture.2016.08.007
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发表时间：
2016-11-01
期刊：
影响因子：
4.5
通讯作者：
Sturm, Armin
中科院分区：
文献类型：
--
作者：
Carmona-Antonanzas, Greta;Humble, Joseph L.;Carmichael, Stephen N.;Heumann, Jan;Christie, Hayden R. L.;Green, Darren M.;Bassett, David I.;Bron, James E.;Sturm, Armin
鲑鱼虱 Lepeophtheirus Salaris (Krøyer, 1837) 是一种体外寄生虫，可引起北半球野生和养殖大西洋鲑鱼 (Salmo salar L.) 的感染。虽然商业海水养殖场的鲑鱼控制越来越多地采用非药物方法，例如降低感染率的网箱设计和通过清洁鱼类进行生物控制，但抗寄生虫药物仍然是有效鱼类保健的必要条件。由于鲑鱼除虱剂的种类有限，而且所有这些除虱剂都已经使用了十多年，据报道不同的产品形成了耐药性。成功的耐药性管理需要可靠的敏感性评估，这通常通过鲑鱼生物测定来实现。这些测试涉及将寄生虫暴露于不同的药物浓度，并且需要大量合适的鲑鱼阶段。本研究报告了一种基于反应时间毒性分析的替代生物测定，并且可以在有限的寄生虫数量下进行。该测定通过从开始暴露于设定药物浓度的时间点开始对测试动物进行重复检查来确定中位有效时间 (ET50)，即 50% 的寄生虫中游泳和/或附着行为受损之前所需的时间。这种实验方法进一步允许通过确定个体的反应时间来估计个体鲑鱼的表观药物敏感性，这在旨在阐明遗传因素与寄生虫药物敏感性表型之间的关联的实验中可能是有用的。使用标准 24 小时生物测定和反应时间毒性测定对三种对甲维盐苯甲酸盐敏感性不同的鲑鱼实验室菌株进行了表征。虽然中位有效浓度 (EC50) 和 ET50 在实验重复之间显示出差异，但这两种类型的生物测定始终能够区分敏感和耐药性鲑鱼实验室菌株。海虱感染给全球鲑鱼养殖业造成巨大损失，据估计全球每年损失超过 3 亿欧元。海虱的控制在很大程度上仍然依赖于化学除虱；然而，化学防治受到抗药性形成的威胁。可以通过不同药物的轮换和战略性实施非药物策略来对抗耐药性。然而，耐药性管理需要可靠、可行的敏感性评估方法。本研究是一份技术说明，介绍了一种海虱敏感性评估的新方法。该方法可应用于农场的敏感性评估，其优点是减少了测试所需的寄生虫。此外，该新方法允许推导寄生虫在药物治疗开始后显示反应所需的时间，从而提供表征个体寄生虫的药物敏感性表型的变量。因此，这里提出的生物测定方法将有助于旨在揭示耐药性遗传决定因素的研究。生物测定用于评估鲑鱼虱（一种商业相关的鱼类寄生虫）的药物敏感性。基于响应时间毒性分析的新型生物测定比标准生物测定所需的测试动物更少。这种新型生物测定进一步可以表征个体寄生虫的药物敏感性表型。
The salmon louse Lepeophtheirus salmonis (Krøyer, 1837) is an ectoparasite causing infections of wild and farmed Atlantic salmon (Salmo salar L.) in the Northern hemisphere. While L. salmonis control at commercial mariculture sites increasingly employs non-medicinal approaches, such as cage designs reducing infection rates and biological control through cleaner fish, anti-parasitic drugs are still a requirement for effective fish health care. With only a limited range of salmon delousing agents available, all of which have been in use for more than a decade, drug resistance formation has been reported for different products. Successful resistance management requires reliable susceptibility assessment, which is usually achieved through L. salmonis bioassays. These tests involve the exposure of parasites to different drug concentrations and require significant numbers of suitable L. salmonis stages. The present study reports an alternative bioassay that is based on time-to-response toxicity analyses and can be carried out with limited parasite numbers. The assay determines the median effective time (ET50), i.e., the time required until impaired swimming and/or attachment behaviour becomes apparent in 50% of parasites, by conducting repeated examinations of test animals starting at the time point where exposure to a set drug concentration commences. This experimental approach further allows the estimation of the apparent drug susceptibility of individual L. salmonis by determining their time to response, which may prove useful in experiments designed to elucidate associations between genetic factors and the drug susceptibility phenotype of parasites. Three laboratory strains of L. salmonis differing in susceptibility to emamectin benzoate were characterised using standard 24 h bioassays and time-to-response toxicity assays. While both the median effective concentration (EC50) and the ET50 showed variability between experimental repeats, both types of bioassay consistently discriminated susceptible and drug-resistant L. salmonis laboratory strains. Infections by sea lice cause significant costs to the global salmon farming industry, which have been estimated to exceed €300 million per year worldwide. Control of sea lice still relies to a significant extent on chemical delousing; however, chemical control is threatened by resistance formation. Resistance can be combated by rotation between different drugs and strategic implementation of non-medicinal strategies. However, resistance management requires reliable and feasible methods of susceptibility assessment. The present study is a technical note introducing a novel approach to susceptibility assessments in sea lice. The method can be applied in susceptibility assessments on farms, where it offers the advantage of a reduced requirement of parasites for testing. In addition, the novel method allows deriving the times of parasite require to show a response after drug treatment has started, thus providing a variable characterizing the drug susceptibility phenotype of individual parasites. Accordingly, the bioassay approach presented here will be useful for studies aiming at unravelling the genetic determinants of drug resistance. Bioassays are used to assess drug susceptibility in the salmon louse, a commercially relevant fish parasite A novel bioassay based on time-to-response toxicity analyses requires fewer test animals than standard bioassays. The novel bioassay further allows characterisation of the drug susceptibility phenotype in individual parasites.
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