Twyla Roscovich: Piscine reovirus—a salmon virus fresh from Norway

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      From the Department of Wild Salmon: Over 90 percent of B.C. farmed salmon are testing positive for a recently imported Norwegian virus that causes lesions in the hearts of salmon. Should we be concerned about its effects on wild salmon, one of B.C.’s most valuable natural resources?

      So we have it, solid evidence in a peer-reviewed scientific paper that the salmon-farming industry appears to have imported an exotic virus considered to be the causative agent of a serious salmon disease. For any who look at the science, it’s pretty hard to deny this one. So far, Fisheries and Oceans Canada has made no statement about this virus that now appears to be widespread in B.C. farmed salmon being raised on the major migration routes of our wild salmon.

      So will the industry get away with this? Will British Columbians just look the other way?

      The piscine reovirus in B.C. was first made public by biologist Alexandra Morton in 2012 when she began sampling salmon in B.C. for European viruses. The reason she went looking for European viruses in the first place was because during the Cohen Commission, she gained access to the previously confidential fish-health files of the provincial farm-salmon veterinarian, Gary Marty.

      In the fish-health reports he provided to the industry, Morton found references to several different European diseases, enough to make her suspicious. She began sending samples of both wild and farmed B.C. salmon to a few different high-profile fish viral labs. Sure enough, she began to receive positive test results for segments of the infectious salmon anemia virus (ISAv), the piscine reovirus (PRV), and salmon alpha virus (SAV). While none of these viruses are reported as natural to B.C., they happen to be some of the most common and devastating viruses in salmon farms in Norway. 

      The most widespread virus Morton finds has been finding is PRV in B.C. farmed salmon—a virus that is described to spread like "wildfire" through a population.  She could only gain access to grocery and sushi farmed salmon for testing, but there she found a staggering infection rate of over 90 percent in the farmed salmon she sampled, all of which had been raised in B.C. waters. PRV is a durable, easily detectable virus that lives a long time after the fish dies, unlike the ISA virus. The latter begins to fragment shortly after the fish dies, making it much more difficult get the whole sequence from store-bought fish.

      After Morton went public with her findings, Marty announced that he had also found very high PRV infection rates in farmed salmon in 2010 (75 percent). Morton lobbied the Cohen Commission to review this new information, because the virus has been reported to weaken a salmon's heart, and many Fraser sockeye reach the river but are unable to swim up it.

      Unfortunately, it was too late. The commission had been officially closed for months, so Justice Bruce Cohen never heard evidence that the vast majority of salmon farms on the Fraser sockeye-migration route are likely infected with PRV. This is significant, considering that nearly all Fraser sockeye must pass by a multitude of farms likely infected with this highly contagious exotic salmon virus.

      There are questions to be answered. How dangerous is this virus? Does it cause disease in B.C.? Did it, in fact, come in eggs imported from Norway?

      Viral diseases are those that are caused by a particular virus. Beginning in 1999, salmon farms in Norway were increasingly being hit with a mysterious heart disease called heart and skeletal muscle inflammation (HSMI). No one knew what was causing it until 2010, when a group of researchers headed by Ian Lipkin, director of Columbia University’s Center for Infection and Immunity, used genome sleuthing to uncover the identity of the causative agent of HSMI: a new virus called piscine reovirus. This finding was subsequently confirmed by another group of researchers in Norway who came to the same conclusion: PRV causes the distinctive heart disease in salmon. Since then, several other studies have been published supporting these findings. (Read the research papers here.)

      HSMI is a serious salmon disease that is now very common in salmon farms in Norway. In fact, in its 2012 annual report, Marine Harvest lists HSMI as the second-leading cause of fish losses for the company. Although the disease may only kill 10 to 20 percent of salmon in a farm, 100 percent can be affected by the heart lesions to varying degrees. HSMI damages the heart and muscle tissue, which interferes greatly with the fish’s ability to absorb oxygen and swim.

      Salmon sick with HSMI swim slowly and often rest against the side of the pens for long periods. It typically takes several weeks for a salmon to recover from this disease. Although it is a problem for the salmon-farming industry, it can live with it because most infected farm salmon eventually do recover. It is alarming, however, to think what HSMI means for wild salmon, which do not have the luxury of resting for weeks while they recover.

      Still, the B.C. salmon-farming industry and government deny that PRV has any connection to HSMI, calling it an “orphan virus”—a virus without a disease—despite the numerous scientific papers that refer to PRV as the "causative agent" of HSMI. 

      We decided the best way to clarify what piscine reovirus means for salmon in B.C. was to go to Norway and interview the scientists who are dealing directly with this virus. In May 2013, I flew to Norway to interview scientists at various universities, vaccine companies, and veterinary associations. My first question was simple: “Does PRV cause HSMI?” Across the board, all the scientists were unanimous in their assertion that piscine reovirus was indeed the causative agent of HSMI. This was from scientists who were working for the industry, some of whom were conducting experiments with the virus by injecting it into the salmon. That was to study the heart lesions in an attempt to develop a vaccine for the industry, and these researchers were oblivious to the controversy about the virus in B.C.

      The next argument given by industry and government in B.C. to explain their lack of action is that perhaps PRV has always been in B.C. and we just never knew it.  However, this doesn’t hold water either. In July 2013, Morton coauthored the first scientific paper on PRV outside of Norway in the Virology Journal. Fred Kibenge, Morton, and others, show that the viral sequences found in Atlantic salmon in B.C. most closely match PRV in infected farmed Atlantic salmon in the Norwegian Lofoten Archipelago, meaning that the virus almost certainly came from Norway. You can't have nearly identical viruses existing in two different oceans. Viruses gradually mutate and the slight changes in the B.C. variant suggest it arrived sometime around 2007.

      If government and industry had a valid disagreement to this published science, they could submit a scientific rebuttal to the Virology Journal

      The real question is: why wouldn’t we have the same European disease as Norway? We have the same companies, farming the same salmon, with the same virus.

      B.C. wild salmon could easily be contracting the virus as juveniles as they pass the farms on their way out to sea. The Norwegian scientists say it takes several months after contracting the virus for the heart damage to develop. By then, the wild salmon would be well on their way to the North Pacific, possibly unable to catch food and escape predators. Millions could be disappearing due to this disease and no one would ever know. It is baffling that no one seems to be paying any attention to this serious threat to one of B.C.’s most important public resources.

      Another aspect to this issue is that this virus is quietly present wherever infected farmed salmon are sold. Since it is such a durable virus, when people wash farmed fillets under running water, PRV could be entering watersheds from the Fraser River to California and Asia. PRV not only infects salmon, but has also been found in herring and trout with unknown consequences.

      The Department of Wild Salmon is asking for the public’s help in stopping this virus from spreading and determining what impacts it may be having on B.C. wild salmon. Although infected fish often show no outer signs, two common symptoms are soft flesh and heart tissue.

      We have created a poster listing a number of fish-disease symptoms that could be linked to European viruses. This poster can be downloaded from our website or we can mail waterproof copies to people interested in putting them up at fish cleaning stations, harbours, marinas, et cetera. To order posters, or for more info on the virus, disease-symptom reporting, and what you can do, visit and the Department of Wild Salmon. Our government’s lack of response is not acceptable, as wild salmon are too valuable.

      Apparently, we need to do this work ourselves.

      Twyla Roscovich is an independent documentary and marine-ecology filmmaker working on the coast of B.C. She directed Salmon Confidential.





      Aug 10, 2013 at 10:25am

      That was not a link to a peer-reviewed scientific paper. It was grey literature at it's finest and slightly above wikipedia. Nice try.

      Martin Dunphy

      Aug 10, 2013 at 12:20pm


      That is a news release. Look in there for the report title at the top.


      Aug 11, 2013 at 12:22pm

      So does the virus infect the food chain? The biggest threat to big business and government is for people to be educated and to know. Are there any more reasons to ban fish farming on BC waters, I think not.

      Ben Sili

      Aug 11, 2013 at 9:13pm

      "The nucleotide sequence data available for PRV are limited, and there is no genetic information on this virus outside of Norway and none from wild fish."

      Meaning there is no way of knowing if this virus is present in wild populations and how it would affect or not these populations in real life, if it is inhibited for instance and salmons are just a carrier etc... So much for the scientific method...

      Paul T

      Aug 12, 2013 at 7:57am

      In the poster you've linked to, you're being slightly disingenuous by holding back some important information. It's not just European viruses that cause those symptoms you've listed. In scientific terms, they aren't pathognomonic. That means that a symptom like pale mushy hearts for example, is not characteristic of one disease. In fact it can be caused by endemic bacteria as well.

      By leaving this information out, you are only contributing to inducing panic. In fact, in your own documentary Twyla, Morton described some of the dead fish found in the BC rivers as symptomatic of Columnaris, a bacteria native to your West Coast.

      It's fine to note the characteristics, and could be helpful depending on how fresh the mortality is. However, it's not on the up and up to leave out important caveats like that I've described above.

      Norway Farmed Public Relations

      Aug 12, 2013 at 8:46am

      A couple of comments seem sponsored by the Farmed Salmon lobby much like the Tobacco Industry in the 60's 7 70's uttering Denials & other BS.

      Virus that infect any species can and do mutate to infect other species and even totally different animals.

      To suggest that Farmed Salmon can not infect wild species of Salmon is simply NOT credible.

      Why are we in Canada allowing a Foreign Corporation to reap profits on the back of our Environment and put at risk our wild fishery?

      What for a few job's and don't tell me about the economic benefits because most of the Profits go OFFSHORE.

      We should BAN Farming of Foreign Fish species not natural to our waters like Atlantic Salmon in Pacific Waters, this is a CLEAR risk to Pacific Salmon species.


      Aug 12, 2013 at 10:24am

      I call Bullscovitch.

      Kim Brokenshire

      Aug 12, 2013 at 5:07pm

      I love the first sentence that starts with "solid evidence" and followed by "appears to have" and "considered to be". Kinda like saying "I know for sure that I don't really know".

      So, after wading through all the "wiggle words" in this opinion piece, we are left with this: no BC salmon (wild, farmed or of hatchery origin) have ever tested positive for the diseases mentioned (ISA or HSMI).

      So all this is, is a scare piece written for someone by someone else because they won't take responsibilty for the law suit they would undoubtedly lose.

      Kim Farmed Salmon Public Relations

      Aug 12, 2013 at 6:32pm

      @Kim..There is very good reason the 'Official' Government Tests do not Test positive for this as follows..

      The Department of Fisheries and Oceans (DFO) and the Canadian Food Inspection Agency (CFIA) do not test for PRV.

      Because any reasonable person knows Politicians are owned by Corporations such as Big Oil & Foreign Multi-Nationals.