| Summary: | Amoebic gill disease (AGD), caused byNeoparamoeba perurans, is a major health challenge for Atlantic salmon aquaculture globally. While freshwater bathing for 2 hr is effective in reducing infection severity, there is need for more rapid and lower cost alternatives. To this end, a combination of sodium percarbonate (SPC) in freshwater was examined for its treatment efficacy. Initial in vitro studies showed a reduction in amoeba viability when exposed for 30 min to freshwater containing >500 mg/L SPC. Subsequently, AGD-affected salmon were bathed for 30 min in 16 degrees C freshwater containing 100, 500 or 1,000 mg/L SPC, or for 2 hr in 16 degrees C freshwater to mimic industry practice. Treatment at the highest SPC concentration caused extensive gill damage and substantial mortality. Neither occurred to a significant extent at lower SPC concentrations. Gill pathology of surviving fish 10 days post-treatment (dpt) was comparable to or more severe than pre-treatment, and significantly (p < .001) more severe than in 2 hr freshwater bathed fish.N. peruransDNA was confirmed by qPCR in all treatment groups at 10 dpt. The data indicate that a 30-min exposure to SPC in freshwater is not a suitable alternative to existing freshwater treatment of AGD.
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