Piscine Reovirus and the Fate of the Wild Pacific Salmon

Piscine Reovirus: Part 1

by Ray Grigg - Shades of Green

If the “research” recommendations of the Cohen Commission Report are to be implemented, then the study of “pathogens” emanating from net-pen salmon farms would be a useful place to begin. Indeed, Justice Cohen is quite explicit that rigorous testing be undertaken on “the hypothesis that diseases are transmitted from farmed salmon” to wild species (Chapter 4, #68, p. 113B).

This is a fertile area for study. For example, Justice Cohen learned during a special reconvening of his Commission in December, 2011, that infectious salmon anemia (ISAv), is a lethal viral infection in wild salmon linked to the arrival of salmon farms to BC's West Coast. Had he chosen to reconvene again four months later at the urging of Alexandra Morton, he would also have learned of another debilitating affliction likely brought to the West Coast by the salmon farming industry. A piscine reovirus (PRV), known to cause heart and skeletal muscle inflammation (HSMI), is a disease that so weakens wild salmon that they may be unable swim the oceans or migrate to their spawning grounds. Although Justice Cohen didn't receive evidence on PRV-HSMI, he already knew enough from his hearings to warn that “devastating disease could sweep through wild [salmon] populations... .”

Just as Justice Cohen anticipated in his Report, the presence of PRV-HSMI in BC's wild salmon was not revealed by the provincial government or the Department of Fisheries and Oceans (DFO), the two agencies that are supposed to be monitoring the condition of marine health. Once again disclosure of PRV-HSMI came from Morton.

The credibility of her April, 2012, findings were supported by Professor Rick Routledge, a Simon Fraser University fish population statistician, whose research team found the piscine reovirus in 13 of 15 Cultus Lake cutthroat trout, a salmonid species (The Vancouver Sun, July 19/12). Such a virus might explain the mysterious collapse of Cultus Lake salmon runs.

Morton discovered PRV-HSMI when she purchased 45 BC-grown farmed Atlantic salmon from supermarkets in Vancouver and Victoria during February, 2012, and sent samples to PEI's Atlantic Veterinary Lab for testing. Of the 45 samples, 44 tested positive for the piscine reovirus known to cause HSMI. The sequenced profile of the virus indicated it was 99 percent identical to the one found in Norwegian farmed salmon. If this reovirus is in BC farmed salmon in such high proportions, it is almost certainly in the wild salmon that swim past the farms on their migration routes, providing the most likely explanation for how the virus got to Cultus Lake cutthroat.

The implications for all salmonids are significant. As Morton explains, “The obvious potential that piscine reovirus is killing Fraser sockeye by weakening their hearts, rendering them less capable of fighting their way through white water rapids like Hell's Gate, was never raised at the [Cohen Commission] Inquiry. Despite the Province of BC apparently knowing it was common in salmon farms.” As Morton contends, this information about PRV-HSMI is vital if we are to explain why “over 90 percent of the Fraser sockeye die as they are swimming upstream.”

Notably, when Dr. Kristy Miller was giving evidence at the reconvened hearings of the Cohen Commission in December, 2011, she did mention that preliminary indications — made independently by her in defiance of DFO instructions to cease investigations — identified piscine reovirus in Chinook salmon in a farm in Clayoquot Sound and in some Fraser River sockeye. Since the focus at the time was on infectious salmon anaemia (ISAv), the evidence of PRV-HSMI seemed to pass as merely incidental information.

But it wasn't incidental information. It was and is extremely relevant, even though the presence of PRV doesn't technically mean the clinical symptoms of HSMI are present. Reports from the provincial veterinarian pathologist lab as early as 2008 showed “congestion and hemorrhage in the stratum compactum of the heart” in farmed salmon, symptoms consistent with PRV-HSMI. And both the pathologist and the industry were aware of 75 percent infections rates of PRV in farmed salmon in 2010. Apparently this information was not conveyed to the Cohen Commission because the pathologist and industry did not consider the reovirus to be a health concern to wild salmon.

However, as Morton has pointed out in her website (alexandramorton.typepad.com), this opinion is contradicted by “a joint scientific publication by the Center for Infection and Immunity, Columbia University, New York, and by Norwegian government scientists” who warn, “It is urgent that measures be taken to control PRV not only because it threatens domestic salmon production but also due to potential for transmission to wild salmon populations.”

This threat was not new information. HSMI was first identified in 1999 in Norwegian salmon farms, according to Brandon Keim, writing in Wired Science on July 13, 2010 (“Salmon Killer Disease Mystery Solved”). He reported that a two year study had determined the cause of HSMI to be a 10-gene piscine reovirus. “Infected fish are physically stunted,” Keim wrote, “and their muscles are so weakened that they have trouble swimming or even pumping blood. The disease is often fatal, and the original outbreak has been followed by 417 others in Norway and the United Kingdom. Every year there's more of the disease and it's now been seen in wild fish, suggesting that farm escapees are infecting already-dwindling wild stocks.” The disease, he noted, spreads like “wildfire” where fish are concentrated in high densities like salmon farms.

From the evidence presented to Justice Cohen, he concluded that such warnings are real and justified, and “that salmon farms along the sockeye migration route have the potential to introduce exotic diseases and to exacerbate endemic diseases...” (Chapter 2, p. 22A). 

“I therefore conclude,” he writes ,“that the potential harm posed to Fraser River sockeye salmon from salmon farms is serious or irreversible” (Ibid.) — a damning finding considering that, in his terminology, “Fraser River sockeye” usually means “all wild salmon”.