Farmed Wild Salmon Virus Came From Atlantic Fish Farms, Study Claims

Evidence reveals that a debilitating virus identified in wild salmon was transferred from B.C. fish farms breeding Atlantic salmon.

The researchers utilized genome sequencing to track down the piscine orthoreovirus (PRV). They claimed the virus was initially brought to British Columbia waters from Norway roughly 30 years ago, at the beginnings of open-net pen aquaculture.

According to the study, the data now implies that the virus is continually shared between farmed and wild Pacific salmon as they travel past the farms. Researchers published the study titled "Aquaculture Mediates Global Transmission of a Viral Pathogen to Wild Salmon" in the peer-reviewed journal Science Advances.

PRV is a disease associated with cardiac and skeletal muscle inflammation in farmed salmon and kidney and liver damage in wild B.C. salmon and has decimated salmon farms in Norway.

Experts from the University of British Columbia and the Strategic Salmon Health Initiative, a collaboration between Fisheries and Oceans Canada, Genome B.C., and the Pacific Salmon Foundation, performed the study.

"One of the cool things about our study is we demonstrate that this genomic technology, which has been developed to survey viral pathogens in humans, can be translated and used to study a really important fishery resource," Dr. Gideon Mordecai, told CBC Canada.

Mordecai, a viral ecologist at the university's department of medicine, said evidence is emerging that B.C. aquaculture facilities transmit the virus to wild salmon. He noted that the infection rates are rising as wild salmon get closer to the farms.

This group, according to Mordecai, "brought" the virus to the area. He went on to say that the high infections in the stocked net pens continue to introduce me, and that this is having an impact.

Viruses Leaving a Genetic Fingerprint

The North Atlantic gave rise to a PRV lineage that is now prevalent in the North East Pacific. According to The Conversation, experts initially discovered the virus in coastal British Columbia waters some 30 years ago. This coincides with the arrival in B.C. of Atlantic salmon eggs from Europe, which aided in the start-up of salmon farming in the province.

Two lines of evidence strongly suggest that the virus is spread between farmed and wild salmon. When wild Chinook salmon were closer to salmon farms, they were more likely to be infected with PRV. A genomic investigation revealed that farmed and wild salmon had the same virus variations, suggesting that transmission is ongoing.

Further examination of PRV genomes in B.C. waterways reveals that the number of PRV infections in the region has grown by two orders of magnitude over the previous two decades, a pattern that corresponds to a regional rise in farms, where virtually all of the fish get sick.

In Atlantic salmon, all versions of the virus, including the PRV identified in B.C., induce cardiac lesions. The same illness linked to PRV has been discovered in Atlantic salmon farms in British Columbia, according to research.

B.C. Salmon Farmers' Association: We Are Not Importing Anything

The B.C. Salmon Farmers' Association said Wednesday that it would look at the report. Still, that archival salmon tissue from 1977 shows PRV was prevalent in B.C. waterways before fish farms were established.

It added in a statement that the PRV strain in B.C. is genetically distinct from the virus in Europe and that the illness did not arrive on the West Coast from Norway, contrary to UBC studies.

"We are not importing anything,"' the statement said per the Vancouver Sun. The farmers' association clarified that the Atlantic salmon they raise in B.C. is raised entirely in their region. According to them, the fish they bred in Vancouver Island hatcheries are broodstock born and nurtured on the island.

The B.C. Salmon Farmers' Association said Wednesday that it would look at the report but that archival salmon tissue from 1977 shows PRV was prevalent in B.C. waterways before they established fish farms.

It added in a statement that the PRV strain in B.C. is genetically distinct from the virus in Europe. The illness did not arrive on the West Coast from Norway, contrary to UBC studies.

The federal Department of Fisheries and Oceans also encourage conducting additional studies to detect better and understand possible concerns connected with PRV strains.

Check out more news and information on Medicine and Health in Science Times.