The European variant of infectious salmon anaemia virus (ISAV) was said to have arrived in British Columbia almost five years ago, but then the Canadian Food Inspection Agency said it was not so after testing two suspect salmon. That was in 2011.
But if British Columbia was ISAV-free then, it almost certainly is not now, according to a study of more than 1,000 farmed and wild fish published Jan. 6 under the title Discovery of variant infectious salmon anaemia virus (ISAV) of European genotype in British Columbia, Canada.
Long thought to be a threat to North Atlantic salmon, ISAV has been on the move, spreading as far as Chili in Atlantic salmon eggs where a decade ago it did $2 billion in damages and outbreaks.
The threat to the BC wild salmon industry, which includes tourism, commercial and sport fishing, could be much larger.
“I have been following this work for many years. ISA virus is a serious matter,” says Daniel Pauly, one of the world’s leading fisheries scientists, based at the University of British Columbia (UBC). “A member of the influenza family in open ocean feedlots is a risk Canada should not be taking on the West Coast.”
The researchers were not allowed access to Atlantic salmon from farms for testing and so all farmed salmon samples came from markets in British Columbia. Detection of the ISA virus was three-fold greater in farmed than wild salmon, but European ISA virus genetic sequence was detected in 72 percent of the cutthroat trout that reside in Cultus Lake, home to Canada’s most endangered Fraser River sockeye salmon population. Government attempts to restore Cultus Lake sockeye with fishing bans and habitat enhancement and restoration have been unsuccessful.
The authors say the study raises the question of whether the ISA virus is impacting Cultus sockeye and other BC wild salmon populations, and if so, at what cost?
“The potential that viruses such as ISAV are contributing to widespread decline in sockeye salmon populations cannot be taken lightly,” states co-author Rick Routledge. “The findings in this paper should lead to development of more sensitive screening for this specific virus. This opportunity needs to be pursued with vigor.”
The study also found evidence of ISA virus in sea lice.
“Finding ISA virus genetic material in a sea louse from a heavily salmon farmed region, the Discovery Islands, significantly elevates my concern that the pathogen release from the open net farming industry is far more serious than anyone knew,” says Craig Orr, Conservation Advisor for Watershed Watch.
“This was a difficult strain of ISAV to detect, because of a small mutation,” says co-author Alexandra Morton. “It is easy to see how it was missed, but we have cracked its code. It is critical that we learn from what happened to Chile. In my view, this work gives BC and our U.S. neighbors the opportunity to avoid tragic consequences.”
A lawsuit has been filed in the U.S. against the U.S. Environmental Protection Agency for allowing wild salmon to be put at risk from farmed salmon diseases.
The researchers published the study in The Virology Journal, a peer-reviewed scientific publication from BioMed Central, a leading academic open access publisher in the areas of biology, medicine and health. BioMed Central is part of global publishing house Springer Nature.© Food Safety News