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Hypoxia tolerance and responses to hypoxic stress during heart and skeletal muscle inflammation in Atlantic salmon (Salmo salar)

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Kjetil Aune


18th International Conference on Diseases of Fish and Shellfish; Belfast, 2017-09-06–2017-09-08

Lund, Morten; Dahle, Maria Krudtaa; Timmerhaus, Gerrit; Alarcon, Marta; Powell, Mark; Aspehaug, Vidar; Rimstad, Espen; Jørgensen, Sven Martin

Introduction Heart and skeletal muscle inflammation (HSMI) is associated with Piscine orthoreovirus (PRV) infection and is an important disease in Atlantic salmon (Salmo salar) aquaculture. Since PRV infects erythrocytes, and farmed salmon frequently experience environmental hypoxia, effects of PRV infection and HSMI on hypoxia tolerance, cardiorespiratory performance and blood oxygen transport were studied. Methodology A cohabitation trial with PRV-infected fish was performed, and one group (PRV-H) was exposed to periodic hypoxic stress for 2h at 40% O2 at 4, 7 and 10 weeks post-infection (WPI). We analyzed the effects of PRV infection on individual incipient lethal oxygen saturation (ILOS) in an hypoxia challenge test (HCT). Maximum heart rate (fHmax), hemoglobin-levels and hemoglobin-oxygen affinity measurements were also performed. Results Periodic hypoxic stress did not influence the infection levels or histopathological changes in the heart. At 7 WPI (peak level of PRV infection) and 10 WPI (peak HSMI pathology) the PRV-infected group exhibited reduced hypoxia tolerance compared to non-infected fish. This was in line with maximum heart rate (fHmax) measurements at 10 WPI, showing a lower temperature optimum (Topt) for aerobic scope for PRV-infected fish, which may indicate reduced cardiac performance and thermal tolerance. Although the PRV-H group had reduced hemoglobin-oxygen affinity compared to non-infected fish, this group performed equal to non-infected fish in hypoxic stress tests and heart rate measurements at 10 WPI, suggesting a preconditioning effect of previous hypoxic stress. Conclusion Hypoxia tolerance and cardiac performance are impaired during HSMI. This effect can be improved by preconditioning from short-term hypoxic stress episodes.