A “new” virus found in BC farmed and wild salmon isn’t so new after all.
Piscine Reovirus (PRV) has been around since at least 1977, according to a new peer-reviewed paper soon to be published in the Journal of Fish Diseases, with Dr. Gary Marty as lead author.
The study tested 363 preserved samples of fish from 1974-2008, and 916 fresh-frozen samples from 2013.
None of the fish showed signs of Heart and Skeletal Muscle Inflammation (HSMI), which some research done in Europe suggests may be linked to PRV.
In the past several years, PRV has been found in wild and farmed BC salmon. Last year, activist Alexandra Morton used this to launch a lawsuit against Marine Harvest Canada, alleging that the company put “diseased fish” into the ocean.
She quickly followed up the lawsuit by co-authoring a study on PRV and HSMI which suggests the version of the virus in BC diverged from the Norwegian strain in 2007, implying, of course, that somehow salmon farms in BC introduced the virus from Norway.
The study was unfortunately rather poor. Its biggest weakness is the small sample size.
- It relies on only 14 samples of fish taken in BC.
- It relies on only 10 samples of Atlantic salmon.
- All of the samples were taken in 2012.
- All of the conclusions about virus divergence are based on computer modelling.
In this study’s conclusion, it states that “Our work suggests PRV entered both Chile and western Canada recently.”
This year’s Marty study shows last year’s PRV study is wrong.
In science, if you make a prediction about how something should work, and that prediction fails, your hypothesis was wrong and you start over.
The predictions made by the study co-authored by Morton are wrong, in light of the new Marty study.
Salmon farms did not introduce PRV to BC; it’s been here for decades and since before the first salmon farm was built, and maybe even longer.
One more tidbit: Marty’s study also showed that archived samples of Alaskan salmon carried PRV, too.
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Local researchers contribute to virus study
Campbell River Mirror, August 12, 2014
Campbell River’s Centre for Aquatic Health Sciences was involved in a new study, published last month in the international peer-reviewed Journal of Fish Diseases, that reports on extensive fish virus research, confirms that the recently-identified fish virus, piscine reovirus, is a benign virus that has long been present in fish in the Pacific Northwest.
The study, titled Piscine reovirus in wild and farmed salmonids in British Columbia, Canada:1974-2013 (G. Marty, D. Morrison, J. Bidulka, T. Joseph, A. Siah, 2014), reports on the results of thousands of fresh and historical salmon tissue samples tested to understand more about the presence of piscine reovirus (PRV) in the Pacific Northwest.
The study concludes that PRV is present in many species of wild-sourced and farm-raised salmon.
The earliest positive result, identified in a wild-source steelhead trout from British Columbia, was from 1977 and predates the start of salmon farming in British Columbia.
Importantly, the study confirms that the fish that carry PRV did not show any signs of disease, such as heart and skeletal muscle inflammation.
http://www.farmfreshsalmon.org/local-researchers-contribute-virus-study
Abstract
Piscine reovirus (PRV) was common among wild and farmed salmonids in British Columbia, western Canada, from 1987 to 2013. Salmonid tissues tested for PRV by real-time rRT-PCR included sections from archived paraffin blocks from 1974 to 2008 (n = 363) and fresh-frozen hearts from 2013 (n = 916). The earliest PRV-positive sample was from a wild-source steelhead trout, Oncorhynchus mykiss (Walbaum), from 1977. By histopathology (n = 404), no fish had lesions diagnostic for heart and skeletal muscle inflammation (HSMI). In some groups, lymphohistiocytic endocarditis affected a greater proportion of fish with PRV than fish without PRV, but the range of Ct values among affected fish was within the range of Ct values among unaffected fish. Also, fish with the lowest PRV Ct values (18.4–21.7) lacked endocarditis or any other consistent lesion. From 1987 to 1994, the proportion of PRV positives was not significantly different between farmed Atlantic salmon, Salmo salar L. (44% of 48), and wild-source salmonids (31% of 45). In 2013, the proportion of PRV positives was not significantly different between wild coho salmon, Oncorhynchus kisutch (Walbaum), sampled from British Columbia (5.0% of 60) or the reference region, Alaska, USA (10% of 58).
http://onlinelibrary.wiley.com/doi/10.1111/jfd.12285/abstract
