Hock Sabrina D, Poulin Robert
Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Int J Parasitol Parasites Wildl. 2012 Nov 15;1:13-8. doi: 10.1016/j.ijppaw.2012.10.002. eCollection 2012 Dec.
Anthropogenic stressors such as pollutants can modulate levels of parasitic infections in aquatic animals by suppressing host immunity or through some other mechanisms. One such mechanism could involve increases in either the quantity or quality of infective stages produced by parasites. We investigated the effect of exposure of infected snails, Potamopyrgus antipodarum, to different concentrations of the widely-used herbicide glyphosate, on (i) the production of infective cercariae by three trematode species, Coitocaecum parvum, Apatemon sp. and an undescribed renicolid, and (ii) the survival of cercariae of the latter species. For all three trematode species, infected snails exposed over a month to low (0.36 mg a.i. L(-1)) or medium (3.6 mg a.i. L(-1)) formulated glyphosate concentrations released between 1.5 and 3 times more cercariae per day than snails under control conditions. The similar pattern seen in all trematodes suggests a general weakening of the host benefiting any of its parasites rather than some parasite species-specific mechanism. In addition, the survival of renicolid cercariae improved with increasing glyphosate concentrations, with cercariae living about 50% longer in the medium concentration (3.6 mg a.i. L(-1)) than in control conditions. Our results demonstrate a clear interaction between glyphosate pollution and parasitism by trematodes in freshwater systems, occurring at glyphosate concentrations recorded in aquatic habitats, and within the environmental exposure limit allowed in New Zealand freshwaters. Future risk assessments and toxicity tests need to consider indirect impacts resulting from infections to invertebrate and vertebrate species penetrated by cercariae and serving as second intermediate hosts of trematodes.
诸如污染物等人为应激源可通过抑制宿主免疫力或其他一些机制来调节水生动物体内寄生虫感染的水平。一种这样的机制可能涉及寄生虫产生的感染阶段数量或质量的增加。我们研究了将受感染的新西兰泥蜗暴露于不同浓度的广泛使用的除草剂草甘膦中，对（i）三种吸虫物种——微小隐尾吸虫、阿帕特蒙吸虫和一种未描述的肾居吸虫——感染性尾蚴的产生，以及（ii）后一种物种尾蚴的存活情况的影响。对于所有三种吸虫物种，暴露于低浓度（0.36毫克有效成分/升）或中浓度（3.6毫克有效成分/升）配方草甘膦一个月的受感染蜗牛，每天释放的尾蚴数量比处于对照条件下的蜗牛多1.5至3倍。在所有吸虫中观察到的类似模式表明，宿主普遍衰弱有利于其任何一种寄生虫，而不是某种寄生虫物种特异性机制。此外，随着草甘膦浓度的增加，肾居吸虫尾蚴的存活率提高，中浓度（3.6毫克有效成分/升）下尾蚴的存活时间比对照条件下长约50%。我们的结果表明，在淡水系统中，草甘膦污染与吸虫寄生之间存在明显的相互作用，这种相互作用发生在水生栖息地记录的草甘膦浓度下，且在新西兰淡水允许的环境暴露限值范围内。未来的风险评估和毒性测试需要考虑感染对作为吸虫第二中间宿主的被尾蚴穿透的无脊椎动物和脊椎动物物种产生的间接影响。
