The physiological cost of a sub-lethal infection with infectious salmon anemia virus (ISAV) in wild Atlantic salmon (Salmo salar)

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University of New Brunswick
Infectious Salmon Anemia Virus (ISAV) is an important pathogen affecting farmed Atlantic salmon and infectious to wild salmon. Wild Atlantic salmon in the outer Bay of Fundy of Canada's East Coast is an important component of biodiversity in aquatic ecosystems and has been endangered since 2010. Here, the effects of sub-lethal ISAV infection are quantified in wild-type Atlantic salmon (Tobique River strain) using an ISAV strain first isolated in Nova Scotia, Canada, in 2012. All fish were intraperitoneally injected with the virus or sham-injected with physiological saline, and anemia caused by ISAV was assessed at intervals using red blood cell count, hematocrit, and hemoglobin concentration. The effects of ISAV infection on metabolic rates at peak infection (16 days post-infection; DPI) and post-peak infection (30 DPI) were measured using wholetank intermittent stop-flow respirometry to obtain post-stress aerobic metabolic scope (PSAMS) and excess post-stress oxygen consumption rates (EXPOC) using a 2-minute net chase as the stressor. No anemia was observed at 16 or 30 DPI. ISAV had no measurable effect on the fish during this experiment. In a separate experiment, ISAV challenged fish kidney tissue was sampled at 7, 17, and 78 DPI, with respective relative viral loads of 104 RNA copies, 105 RNA copies, and 103.08 RNA copies. The effects of sub-lethal ISAV infection on the protein synthesis/degradation cycle was measured. Anemia was observed at 7 and 17 DPI in ISAV infected fish for this experiment, and protein synthesis rates were higher in ISAV+ fish compared to sham-injected controls at 7 DPI (7.51 ± 1.75 %/day; p = 0.001) and 17 DPI (7.65 ± 1.73 %/day; p = 0.06).