An Atypical Course of Cardiomyopathy Syndrome (CMS) in Farmed Atlantic Salmon ( Salmo salar ) Fed a Clinical Nutrition Diet

• Published in: Microorganisms
• Main Authors: Johan Rennemo, Kjetil Berge, Muhammad Naveed Yousaf, Tommy Berger Eriksen, Eirik Welde, Camilla Robertsen, Bjarne Johansen, Charles McGurk, Espen Rimstad, Erling Olaf Koppang, Håvard Bjørgen
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2023
• Subjects: clinical nutrition; CMS; fish health; fish welfare; PMCV; population medicine; Biology (General); QH301-705.5; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.3390/microorganisms12010026; https://doaj.org/article/1c9fc609a4ba4b4d8ed681cd878bfc78

Cardiomyopathy syndrome (CMS) poses a significant threat to farmed Atlantic salmon ( Salmo salar ), leading to high mortality rates during the seawater phase. Given that controlled experimental challenge trials with PMCV do not reproduce the mortality observed in severe field outbreaks of CMS, field trials on natural CMS outbreaks are warranted. This field study explored the impact of a clinical nutrition intervention, specifically a diet enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on a severe CMS outbreak in a commercial sea farm. CMS was diagnosed in a single sea cage with high mortality rates. Histopathological analysis, RT-qPCR in situ hybridization for virus detection, and fatty acid composition analysis were used to monitor the impact of disease and the inclusion of EPA and DHA in heart tissue. Following the implementation of clinical nutrition, a decline in mortality rates, regression of CMS-associated changes, and a significant reduction in piscine myocarditis virus (PMCV) RNA load were observed within the salmon population. Fatty acid composition analysis of heart samples demonstrated increased levels of EPA and DHA, reinforcing the association between dietary factors, viral load dynamics, and overall fish health. Although further validation is needed in future studies, as field trials may not be sufficient to establish causation, our results indicate that optimizing the EPA + DHA levels may prove beneficial in severe CMS outbreaks.