Assessing peracetic acid as a means to control post-vaccination Saprolegniasis in Atlantic salmon Salmo salar parr in recirculation aquaculture systems

Authors: GOOD, CHRIS - Freshwater Institute; DAVIDSON, JOHN - Freshwater Institute; Straus, David - Dave; Harper, Susan; Marancik, David; Welch, Timothy - Tim; LEPINE, CHRISTINE - Freshwater Institute; Wolters, William; Peterson, Brian; PEDERSEN, LARS-FLEMMING - Technical University Of Denmark; PHUNTAMART, VIPAPORN - Bowling Green State University; SUMMERFELT, STEVEN - Freshwater Institute

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: 9/22/2016
Publication Date: 1/19/2017
Citation: Good, C., Davidson, J., Straus, D.L., Harper, S.B., Marancik, D.P., Welch, T.J., Lepine, C., Wolters, W.R., Peterson, B.C., Pedersen, L., Phuntamart, V., Summerfelt, S. 2017. Assessing peracetic acid as a means to control post-vaccination Saprolegniasis in Atlantic salmon Salmo salar parr in recirculation aquaculture systems [abstract]. Aquaculture America Conference 2017, Feb 19-22, 2017, San Antonio, TX. p. 153.

Interpretive Summary:

Technical Abstract: Land-based closed containment facilities, utilizing recirculation aquaculture system (RAS) technologies, can reduce or eliminate the introduction of obligate fish pathogens. Regardless, the presence of opportunistic pathogens must be assumed, and these agents can cause disease during unfavorable conditions. One such disease, saprolegniasis (caused by Saprolegnia spp. oomycetes), is associated with enormous losses in aquaculture; it is estimated that 10% of all hatched farmed Atlantic salmon Salmo salar die from saprolegniasis. This disease is often observed subsequent to vaccination. Because Atlantic salmon smolt production is increasingly being carried out in RAS, control strategies must be designed to minimize impacts on biofiltration. We investigated daily peracetic acid (PAA) treatments to determine their efficacy in reducing post-vaccination saprolegniasis while assessing biofilter performance in replicated RAS. Twelve replicated experimental-scale RAS were stocked with Atlantic salmon parr (200 fish per RAS, 94g mean weight); fish were subsequently vaccinated with a commercial salmon vaccine via intracoelomic injection. Daily pulse treatments with PAA – i) 0.2 mg/L, ii) 0.5 mg/L, iii) 1.0 mg/L, or iv) deionized water (control) – were administered to culture tank water for six weeks post-vaccination. During this period, data were collected on mortalities and incidence of clinical saprolegniasis, Saprolegnia spp. colony counts from RAS water samples, histopathology of gill, spleen, and kidney tissues, and biofiltration as measured by total ammonia nitrogen (TAN) removal efficiency. Welfare was assessed by examining fish for gross lesions and fin erosion, hemorrhage, and visible Saprolegnia spp. infection. Ultimately, no major post-vaccination Saprolegnia spp.-associated mortality was observed in this study; however, survival was statistically (p<0.05) lower in control parr, and clinical saprolegniasis was significantly more prevalent in the control group. Conversely, PAA treatment was associated with significantly lower fish weight by study’s end. Biofilter TAN removal efficiency was not impacted by PAA administration at all dosages. Water sample plate counts of Saprolegnia spp. colonies increased over time in all treatment groups during the post-vaccination period. Welfare assessments indicated that PAA treatment was significantly protective against observable pectoral fin saprolegniasis and hemorrhage; however, fin erosion in general was not associated with PAA treatment. Histopathology data are currently forthcoming. Overall, results suggest that daily low-dose PAA application can be effective in reducing post-vaccination saprolegniasis in Atlantic salmon while not significantly impacting RAS biofiltration. Further research, however, is necessary to refine PAA dosage and to assess its effectiveness in controlling saprolegniasis in commercial settings.