Understanding the net effects of pesticides on amphibian trematode infections
Understanding the net effects of pesticides on amphibian trematode infections
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DOI：
10.1890/07-1429.1
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发表时间：
2008-10-01
影响因子：
5
通讯作者：
Hudson, Peter J.
中科院分区：
文献类型：
--
作者：
Rohr, Jason R.;Raffel, Thomas R.;Hudson, Peter J.
人为因素可以同时对寄生虫传播产生积极和消极影响，因此量化其对疾病风险的净影响非常重要。净效应将是生存和性状变化的产物（e。例如，在一个实施例中，易感性、感染性）。在单独的实验室实验中，我们暴露了三卷棘口吸虫的尾蚴及其第一和第二中间宿主蜗牛（Planorbella trivolvis）和绿色青蛙蝌蚪（蛙clamitans），分别对四种常见农药之一（阿特拉津，草甘膦，西维因，马拉硫磷）在标准化，生态相关浓度（201.0，3700.0，33.5，和9.6微克/升）。我们测量了农药暴露对这种宿主-寄生虫相互作用的六种重要机制的影响：（1）E. 26小时内的三卷尾蚴，（2）两周内的蝌蚪存活，（3）四周内的蜗牛存活，（4）蜗牛生长和繁殖力，（5）尾蚴感染性，和（6）蝌蚪对固定数量的尾蚴的敏感性。农药，一般来说，造成显着更大的死亡率E。与对照处理相比，阿特拉津对三卷尾蚴的毒性更大，但阿特拉津是唯一一种显著降低尾蚴存活率的化学品（半数致死浓度值为267毫克/升），而且只有在浓度高于水生生态系统中常见的浓度（>= 200微克/升）时才会显著降低尾蚴存活率。没有一种农药显著提高E. trivolvis毒力，蝌蚪存活率降低，或蜗牛存活率、生长或繁殖力降低。亚致死剂量暴露尾蚴4 h对吸虫在R.蛤蚌相反，亚致死暴露R.根据成囊尾蚴的百分比测量，蛤蚌对四种杀虫剂中的每一种的敏感性增加。由于农药诱导的尾蚴死亡率（密度介导的影响），减少接触吸虫小于农药诱导的两栖动物易感性增加（性状介导的影响），这表明暴露于环境现实水平的农药的净效应将提高两栖动物吸虫感染。这些研究结果强调了阐明人为因素对宿主和寄生虫的致死和亚致死效应的重要性，以了解寄生虫传播和毒力变化的机制，这是两栖动物特别需要的方法，两栖动物是一种经历全球疾病相关下降的类群。
Anthropogenic factors can have simultaneous positive and negative effects on parasite transmission, and thus it is important to quantify their net effects on disease risk. Net effects will be a product of changes in the survival and traits (e. g., susceptibility, infectivity) of both hosts and parasites. In separate laboratory experiments, we exposed cercariae of the trematode Echinostoma trivolvis, and its first and second intermediate hosts, snails (Planorbella trivolvis) and green frog tadpoles (Rana clamitans), respectively, to one of four common pesticides (atrazine, glyphosate, carbaryl, and malathion) at standardized, ecologically relevant concentrations (201.0, 3700.0, 33.5, and 9.6 mu g/L, respectively). We measured effects of pesticide exposure on six mechanisms important to this host-parasite interaction: (1) survival of E. trivolvis cercariae over 26 hours, (2) tadpole survival over two weeks, (3) snail survival over four weeks, (4) snail growth and fecundity, (5) cercarial infectivity, and (6) tadpole susceptibility to a fixed number of cercariae. Pesticides, in general, caused significantly greater mortality of E. trivolvis cercariae than did control treatments, but atrazine was the lone chemical to significantly reduce cercarial survival (LC50 value 267 mg/L) and then only at concentrations greater than commonly found in aquatic ecosystems (>= 200 mu g/L). None of the pesticides significantly enhanced E. trivolvis virulence, decreased tadpole survival, or reduced snail survival, growth, or fecundity. Sublethal exposure of the cercariae to the pesticides (4 h) did not significantly affect trematode encystment in R. clamitans. In contrast, sublethal exposure of R. clamitans to each of the four pesticides increased their susceptibility as measured by the percentage of cercariae that encysted. The reduction in exposure to trematodes due to pesticide-induced cercarial mortality (a density-mediated effect) was smaller than the pesticide-induced increase in amphibian susceptibility (a trait-mediated effect), suggesting that the net effect of exposure to environmentally realistic levels of pesticides will be to elevate amphibian trematode infections. These findings highlight the importance of elucidating the lethal and sublethal effects of anthropogenic factors on both hosts and parasites to understand the mechanisms underlying changes in parasite transmission and virulence, an approach that is especially needed for amphibians, a taxon experiencing global disease-related declines.