Dr. Kristi Miller. (Photo: Salmon Confidential)
This research, led by Fisheries and Oceans Canada’s (DFO) Dr. Kristi Miller, was undertaken as part of the Strategic Salmon Health Initiative (SSHI), a collaboration between DFO, the Pacific Salmon Foundation and Genome British Columbia to better understand the distribution of microbes and diseases in wild and cultured (hatchery and aquaculture) salmon in BC.
Dr. Miller pointed out that pathologists found lesions on salmon on one farm in Johnstone Strait indicating they had heart and skeletal muscle inflammation.
”These lesions were present for an extended period of time, at least eight months, on this farm,” Miller said.
The disease has been found in several countries, including Norway in the late 1990s, where it has been linked to low levels of mortality, with some farms showing no salmon deaths, while up to 20 per cent of fish die in others.
Dr. Miller explained that the piscine reo-virus has been associated with all outbreaks of heart and skeletal muscle inflammation, as it was on the single BC farm, but it’s not known if it causes the disease, adding scientists around the world are investigating how the virus could be linked to the disease.
Miller stressed that the fact that many fish can carry the virus without having the disease has been one of the difficulties in understanding the role of this virus in HSMI development and added that the virus likely originated in the marine environment.
”We know that this virus, in other parts of the world, can be observed in fresh-water origin fish and we believe we know that here in BC in Atlantic salmon. But in Norway, while the virus can be observed in fish in hatcheries the prevalence of the virus can become much, much higher in the marine environment,” the scientist highlighted in statements expressed to the Canadian Press.
Heart and skeletal muscle inflammation in fish does not impact human health, and the disease has never been found in wild Pacific salmon.
”But DFO will continue to monitor the health of wild and farmed salmon in Canada and to track and collaborate with international research teams to more fully establish the risk factors associated with this disease,” Miller said.
The research using new technology and international scientists was done between 2013 and 2015 on four Vancouver Island fish farms using more than 2,400 live and dying salmon.
For his part, Brian Riddell, president of the Pacific Salmon Foundation, which participated in the research along with Genome British Columbia, said the latest technology will allow scientists to analyze 45 microbes for the first time, leading to ”revolutionary” diagnostics in wild populations.
”We are currently in the second phase of the analyses and we really just started this so I really have to emphasize the real concern that many people have in BC about the risk of wild salmon. We cannot comment on that yet,” Riddell said, adding more findings will be revealed in the next two years.
”Government and industry should expedite the science, provide necessary funding and work collaboratively for the sake of the aquaculture industry and for wild salmon,” theBC Salmon Farmers Association said in a news release.
HSMI first emerged in Norwegian fish farms around 1999 and ten years later, it expanded geographically and accounted for 150 costly disease outbreaks a year with significant mortality on fish farms. The Norwegian Food Safety Authority made HSMI a reportable disease in 2008. It is not yet a reportable disease in Canada.
Meanwhile, the 2015 annual report of Marine Harvest, one of the world’s largest seafood companies, rates HSMI as the number three cause of mortality in its fish farms, which operate in Norway, Chile, Scotland, Ireland and British Columbia.
Although the DFO scientists noted that ”any role of PRV in the development of HSMI remains unclear,” Norwegian pathologists and veterinarians commonly describe it as the central virus associated with significant and serious HSMI disease in Norway’s fish farms.