Researchers at a news conference in Vancouver disclosed that a lethal and highly contagious marine virus has been detected for the first time in wild salmon in the Pacific Northwest.
The virus, “infectious salmon anemia”, which does not affect humans, was found in 2 of 48 juvenile fish collected as part of a study of sockeye salmon in Rivers Inlet, on the central coast of British Columbia. The study was initiated after scientists observed a decline in the number of young sockeye.
Until now, the virus has never been confirmed on the West Coast of North America. Aqua farms contaminated by the virus have lost 70 percent or more of their fish.
According to the New York Times, Richard Routledge, an environmental scientist at the university who leads the sockeye study, suggested the virus had spread from the province’s aquaculture industry, which has imported millions of Atlantic salmon eggs over the last 25 years from Iceland and Scandinavia.
Routledge admits that no direct evidence of that link existed, but notes that the two fish had tested positive for the European strain of infectious salmon anemia.
“The virus could have a devastating impact not just on the region’s farmed and wild salmon but on the many species that depend on them in the food web, like grizzly bears, killer whales and wolves,” said Dr. Routledge. “No country has ever gotten rid of it once it arrives.”
At the news conference Routledge adds the only barrier between the salmon farms and wild fish is a net, clearing the way for pathogens to circulate in and out. And no vaccine or treatment exists for infectious salmon anemia.
Dr. Gary Marty, the fish pathologist for the province’s Ministry of Agriculture, echoed the British Columbia Salmon Farmers Association’s claim that fish health departments had regularly tested for the virus on the farms and have never found a positive case.
The sockeye samples were collected by Alexandra Morton, an activist and vocal critic of salmon farming practices in British Columbia; Morton says the virus is a cataclysmic threat to both salmon and herring, which can also contract it.
“If we test five million fish and found two sick, O.K.,” said Morton. “But 48 in the middle of nowhere?”
James Winton, who leads the fish health research group at the Western Fisheries Research Center in Seattle, an arm of the United States Geological Survey, referred to this event as a “disease emergency” and urged that research begin at once to determine on how far the virus had spread.
The NYTimes notes that according to the CDC, infectious salmon anemia virus transformed from a benign form in nature into a “novel virulent strain” when salmon stocks entered Norway’s densely packed salmon farms.
A sick fish would experience a slow death in a crowded pen, shedding virus particles, instead of consumed by a predator. Offshore saltwater pens supply most of the Atlantic salmon sold in the United States.
2010 Deadly Epidemic in Farmed Atlantic Salmon
Last year, ScienceDaily reported that a deadly and mysterious epidemic threatened “farmed” Atlantic salmon. According to the Norwegian University of Science and Technology, escaped fish from Norwegian salmon farms interbred with wild salmon, and changed the genetic composition of the country’s wild salmon stocks.
“In rivers that have been affected by diseases or by parasites…wild salmon stocks are weakened and are particularly vulnerable. It is easy for these stocks to be affected by wild salmon whose genes have been diluted by farmed fish.”
The deadly salmon epidemic was identified as heart and skeletal muscle inflammation (HSMI), an often fatal disease first detected in salmon on a farm in Norway in 1999, and reported in 417 fish farms in Norway as well as in the United Kingdom. The disease destroys heart and muscle tissue and kills up to 20 percent of infected fish.
In 2010, an international team claimed the disease may have been caused by a previously unknown virus, and said the “newly identified virus is related but distinct from previously known reoviruses, which are double-stranded RNA viruses that infect a wide range of vertebrates.”
The full study findings were published online in the publication PLoS ONE.