Peracetic acid as a potential treatment for amoebic gill disease (AGD) in Atlantic salmon

The project investigated the potential of peracetic acid (PAA) as a treatment for amoebic gill disease (AGD) in Atlantic salmon. A series of studies were performed to 1) investigate the decay of PAA and the factors that influence this inherent chemical behaviour, 2) document the health and welfare consequences of using PAA in salmon smolts, and 3) evaluate the amoebicidal activity of PAA and its efficacy to treat AGD. Temperature, salinity, light and UV affected the decay dynamics of PAA. Salmon smolts could tolerate PAA doses of 0.6 to 10 ppm, however, behavioural and physiological responses were significantly influenced by duration and frequency of exposure, as well as with PAA commercial products. Stress and disease status of fish were documented to influence the responses of salmon to PAA. The application of PAA was identified to be a mild stressor and could induce both transient and systemic oxidative systems. Different physiological adaptive responses were mounted by the fish to counteract these impacts. PAA exhibited amoebicidal activity in vitro. Exposure of AGD-affected salmon to PAA using different treatment protocols resulted in an equivocal disease resolution. Though treatment could reduce parasite load, gross and microscopic pathologies persisted after the treatments. New insights about the pathophysiology of AGD had been generated particularly on the role of oxidative stress and circulating metabolites. Additional treatment optimisation is required for PAA as a treatment for AGD. Nonetheless, the project provided significant advancements in the chemistry and physiology of PAA in fish that will be crucial in developing the evidence-driven application of this disinfectant in aquaculture.