SINTEF Ocean, Trondheim, Norway.
Norwegian Institute for Water Research, Bergen, Norway.
PLoS One. 2018 Jul 6;13(7):e0199842. doi: 10.1371/journal.pone.0199842. eCollection 2018.
This study examines the potential implications of biofouling management on the development of an infectious disease in Norwegian farmed salmon. The hydroid Ectopleura larynx frequently colonises cage nets at high densities (thousands of colonies per m2) and is released into the water during regular in-situ net cleaning. Contact with the hydroids' nematocysts has the potential to cause irritation and pathological damage to salmon gills. Amoebic gill disease (AGD), caused by the amoeba Paramoeba perurans, is an increasingly international health challenge in Atlantic salmon farming. AGD often occurs concomitantly with other agents of gill disease. This study used laboratory challenge trials to: (1) characterise the gill pathology resulting from the exposure of salmon to hydroids, and (2) investigate if such exposure can predispose the fish to secondary infections-using P. perurans as an example. Salmon in tanks were exposed either to freshly 'shredded' hydroids resembling waste material from net cleaning, or to authentic concentrations of free-living P. perurans, or first to 'shredded' hydroids and then to P. perurans. Gill health (AGD gill scores, non-specific gill scores, lamellar thrombi, epithelial hyperplasia) was monitored over 5 weeks and compared to an untreated control group. Nematocysts of E. larynx contained in cleaning waste remained active following high-pressure cleaning, resulting in higher non-specific gill scores in salmon up to 1 day after exposure to hydroids. Higher average numbers of gill lamellar thrombi occurred in fish up to 7 days after exposure to hydroids. However, gill lesions caused by hydroids did not affect the infection rates of P. perurans or the disease progression of AGD. This study discusses the negative impacts hydroids and current net cleaning practices can have on gill health and welfare of farmed salmon, highlights existing knowledge gaps and reiterates the need for alternative approaches to net cleaning.
本研究探讨了生物污垢管理对挪威养殖三文鱼中传染病发展的潜在影响。水螅 Ectopleura larynx 常高密度（每平方米数千个群体）殖民于网笼，并在定期原位网清洁时释放到水中。与水螅刺细胞接触有可能刺激和引起三文鱼鳃的病理损伤。由变形虫 Paramoeba perurans 引起的阿米巴性鳃病（AGD）是大西洋鲑鱼养殖中日益国际化的健康挑战。AGD 常与其他鳃病病原体同时发生。本研究使用实验室挑战试验：（1）描述三文鱼暴露于水螅后引起的鳃病理变化，（2）以 P. perurans 为例，研究这种暴露是否会使鱼类易受继发感染。水槽中的三文鱼要么暴露于类似于网清洁废物的新鲜“切碎”水螅，要么暴露于真实浓度的自由生活的 P. perurans，要么先暴露于“切碎”水螅，然后暴露于 P. perurans。在 5 周内监测鱼的鳃健康（AGD 鳃评分、非特异性鳃评分、瓣状血栓、上皮增生），并与未经处理的对照组进行比较。高压清洁后，清洁废物中的 E. larynx 刺细胞仍然保持活性，导致暴露于水螅后 1 天内三文鱼的非特异性鳃评分更高。暴露于水螅后 7 天内，鱼的平均鳃瓣状血栓数量更高。然而，水螅引起的鳃损伤并未影响 P. perurans 的感染率或 AGD 的疾病进展。本研究讨论了水螅和当前网清洁实践对养殖三文鱼鳃健康和福利的负面影响，强调了现有知识差距，并再次强调需要替代网清洁方法。
