Research in May conducted as part of the ongoing Strategic Salmon Health Initiative (SSHI) found what is possibly the first case of heart and skeletal muscle inflammation (HSMI) disease in farmed salmon in British Columbia, but a question that is yet to be answered is whether the Piscine Reo-Virus, or PRV, actually causes the disease.
“There's a pretty good weight of evidence that [PRV] is certainly a factor in the development of HSMI in Atlantic salmon. But what other triggers may be required isn't really well understood," leading genomic researcher Kristi Miller-Saunders, who is with Fisheries and Oceans Canada (DFO), told CBC News.
HSMI is a disease that can cause low-level mortalities in farmed Atlantic salmon in Norway. It often found in fish that also carry the Piscine Reovirus, but there is still no definitive evidence of cause and effect. HSMI only affects fish and poses no risk to human health. Prior to this case, examination of thousands of fish from Alaska to Washington State had found no evidence of HSMI in wild or farmed fish on the West Coast of North America.
PRV is an endemic virus in both the Atlantic and Pacific Oceans, found in Alaska, BC, Washington State, Chile and Europe, although research shows differences between the Pacific and European strains. PRV is commonly present on farmed and wild salmon in the Pacific, and is often present in fish that show no signs of ill health. In the researchers’ report, they state that “There is no evidence, to date, that PRV causes any disease in BC Pacific salmon.” Details of the report are at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0141475.
“This disease is particularly difficult to understand. PRV has not been 100 percent confirmed as a cause of HSMI but there has not been a case of HSMI without PRV,” Miller-Saunders told Aquaculture North America (ANA). However, PRV has also been found in fish that have no clinical signs of the disease, leaving its role in disease conditions, such as HSMI, unknown.
First suspected case of HSMI in BC farmed salmon
A team of international researchers led by DFO’s Miller-Saunders found a potential HSMI case in farmed Atlantic salmon samples collected from a BC aquaculture facility in 2013-2014. The facility was announced at first as one “located in the Johnstone Strait” by DFO spokeswoman Michelle Rainer. Cermaq Canada later announced that the samples came from their Venture Point farm.
“Cermaq Canada’s Venture Point farm participated in the collection program, along with three other farm sites operated by Cermaq and Marine Harvest. The scientists concluded that some samples from 2013 at the Venture Point farm have been considered as being consistent with HSMI findings,” said the company.
In total, around 2,500 fish were sampled from four farms between 2013-2015. Only 3 percent of the fish were suspected to have HSMI.
DFO said in a press release in May that the findings are presently limited to a single farm. “DFO is now taking steps to better understand what these findings mean and to map a way forward.”
SSHI scientists continue to test samples from additional farms. Testing is expected to take another three years. Both moribund and live fish have been collected throughout the full production cycles of multiple farms throughout British Columbia. Distribution and prevalence of microbes within the samples hopefully will shed some light on the potential implications of interactions between wild and cultured stock within BC.
Meanwhile, in July, actress and PETA spokesperson Pamela Anderson and environmentalist David Suzuki backed activist Alexandra Morton and the Sea Shepherd Society’s campaign to “conduct audits” of various BC salmon farms. The BC Salmon Farmers Association (BCSFA) dismissed the campaign as a stunt. “We’re disappointed that this latest publicity stunt is attempting to paint a misleading picture of an industry that provides a healthy, sustainable product that feeds millions of people,” said BCSFA executive director Jeremy Dunn.
Salmon health initiative: A long way to go
The Strategic Salmon Health Initiative (SSHI) was launched in 2013 to better understand the presence and distribution of microbes that may impact the health of both wild and cultured salmon in British Columbian waters. Concerns have been raised about high mortalities of juvenile wild salmon during their early migration and the possible impacts salmon farms may be playing. However, there is a wide gap in current knowledge about what microbes are currently present in both wild and cultured salmon within BC and the distribution of diseases affecting them.
SSHI is a collaboration between the Department of Fisheries and Oceans Canada (DFO), the Pacific Salmon Foundation and Genome BC. The initiative has been broken down into four phases and it is expected to take eight years to complete. The project is currently in the second phase and approximately $9 million has been spent to date.
During the initial part of Phase 2 a novel platform was tested and evaluated for its ability to be used in further stages of the project. Test results were evaluated and scrutinized by the Canadian Science Advisory Secretariat and it is currently being used along with the World Organization of Animal Health (OIE) recommended assays allowing testing of up to 45 microbes from a single sample. Use of this micro platform has allowed more widespread testing of many different microbes in a much shorter time period than previous methods allowed.
Sample collection occurred over a year and half within the first phase of the SSHI and consisted of both live and moribund fish from locations across British Columbian marine sites. Although testing of wild fish is considered an important part of examining the microbes and diseases impacting Pacific salmon, collecting wild fish samples is more complicated than that of farmed fish. Wild fish samples are limited to live and relatively healthy fish as moribund and sick fish typically end up as food for predators. This may impact the accuracy of testing for abundance and prevalence of microbes and diseases across wild fish populations. SSHI has several years left until completion and numerous tests left to run. However, reporting is done biannually and results will be released as important findings are discovered.
— Amanda Bibby