In recent days, Marine Harvest Canada has responded to a few email inquiries regarding a fish virus known as the piscine reovirus. We’d like to share the facts about the piscine reovirus (PRV) with our blog readers.
Due to its recent description in science and the availability of new testing methods, PRV is relatively new to fish health research (Palacios et al, PloS One 5(7): 2010). So far, study indicates that in British Columbia (BC) it occurs in wild salmonids (K. Miller[i], R. Routledge[ii]) and farm-raised salmon (G. Marty[iii]).
PRV was first identified in Norway, but that does not mean that it has newly appeared in BC; only that our ability to detect it is new. Nor does its subsequent discovery in BC imply that it was transferred here. It is just as likely to have been here but previously undetected.
Despite some claims, it is incorrect to state that PRV is known to be the causal agent of Heart and Skeletal Muscle Inflammation (HSMI). If that were true, most or all fish with abundant PRV would also have HSMI. In Norway, fish with HSMI often have PRV, but many fish with PRV never develop HSMI. PRV is present in fish in BC, but no farm-raised or wild salmon have been diagnosed with HSMI. The records released during the Cohen Commission’s Inquiry into Fraser River sockeye also support this view.
There is some debate about the relation of PRV and HSMI in Norway, but even recent papers there state that detection of PRV alone does not establish an HSMI diagnosis (Garseth et al. Journal of Fisheries Research: 2012). If PRV was capable of causing harm to our fish or having the potential to cause harm to wild salmon we would take immediate steps to eliminate the virus.
Fisheries and Oceans Canada and the Canadian Food Inspection Agency do not have PRV on the list of reportable diseases/pathogens. At the present time PRV appears to be a benign virus that may have been long present in the world’s oceans.
The practices and fish health records of fish monitoring presented by BC salmon farmers at the Cohen Inquiry impressed the authors of Technical Reports 5A-D and led Justice Cohen to recommend that fish health data reporting continue in order to remove any limitation on determining statistical correlation imposed by the existing 6 year time series. We are continuing to report fish health information towards the additional 10 years of data that the Cohen report recommended.
Marine Harvest is a participant in the new Genome BC project that aims to “explore the transmission dynamics and historical presence of detected microbes, with key focus on microbes that are suspected globally to be causing disease in salmon”. We are pleased to be an active participant in this work as we respect and value the health of both the fish we produce, and the wild fish that inhabit the waters and the environment.