Taylor Richard S, Slinger Joel, Stratford Chris, Rigby Megan, Wynne James W
CSIRO Agriculture and Food, Castray Esplanade, Hobart, TAS 7000, Australia.
CSIRO Agriculture and Food, Bribie Island Research Centre, Woorim, QLD 4507, Australia.
Microorganisms. 2021 Apr 29;9(5):967. doi: 10.3390/microorganisms9050967.
Freshwater bathing for 2-3 h is the main treatment to control amoebic gill disease of marine-farmed Atlantic salmon. Recent in vitro studies have demonstrated that amoebae () detach when exposed to freshwater and that some eventually reattach to culture plates when returned to seawater. Here, we evaluated the potential for gill-detached to survive a commercially relevant treatment and infect AGD-naïve fish and whether holding used bathwater for up to 6 h post treatment would lower infectivity. AGD-affected fish were bathed in freshwater for 2 h. Naïve salmon were exposed to aliquots of the used bathwater after 2, 4, 6 and 8 h. The inoculation was performed at 30 ppt for 2 h, followed by gradual dilution with seawater. Sampling at 20 days post inoculation (dpi) and 40 dpi confirmed rapid AGD development in fish inoculated in 2 h used bathwater, but a slower AGD development following exposure to 4 h bathwater. AGD signs were variable and reduced following longer bathwater holding times. These results suggest that viable amoebae are likely returned to seawater following commercial freshwater treatments, but that the risk of infection can be reduced by retention of bathwater before release.
淡水浸泡2 - 3小时是控制海水养殖大西洋鲑鱼阿米巴鳃病的主要治疗方法。最近的体外研究表明，阿米巴原虫（）在接触淡水时会脱离，并且一些在回到海水后最终会重新附着在培养皿上。在此，我们评估了脱离鳃部的阿米巴原虫在商业相关治疗后存活并感染未感染阿米巴鳃病的鱼的可能性，以及处理后保留用过的浴水长达6小时是否会降低感染性。受阿米巴鳃病影响的鱼在淡水中浸泡2小时。未感染的鲑鱼在2小时、4小时、6小时和8小时后接触用过的浴水的等分试样。接种在30ppt下进行2小时，然后用海水逐渐稀释。接种后20天（dpi）和40 dpi取样证实，接种2小时用过的浴水的鱼中阿米巴鳃病迅速发展，但接触4小时浴水后阿米巴鳃病发展较慢。随着浴水保存时间延长，阿米巴鳃病症状多变且减轻。这些结果表明，在商业淡水处理后，活的阿米巴原虫可能会回到海水中，但通过在排放前保留浴水可以降低感染风险。
