Salmon virus found in Cultus trout samples

Research points to discovery of a new European strain of infectious salmon anemia virus (ISAV) but salmon farmers and expert disagree

The findings of a new study that shows the presence of a salmon virus in B.C. may provide insight into impacts on Cultus Lake sockeye

The findings of a new study that shows the presence of a salmon virus in B.C. may provide insight into impacts on Cultus Lake sockeye

A new study shows high concentrations of a variant of the most feared salmon virus in the world have been detected in Cultus Lake fish.

A scientific paper published last week in the Virology Journal said the discovery of a new European strain of infectious salmon anemia virus (ISAV) was confirmed after tests on more than 1,000 farmed and wild fish, including cutthroat trout samples from Cultus Lake.

The findings may provide new insight into impacts on Cultus Lake sockeye, considered Canada’s most endangered Fraser River sockeye population, say report authors, including researchers Alexandra Morton and Dr. Rick Routledge.

Although detection of the ISA virus was three-fold greater in farmed salmon compared to wild salmon, the European ISA virus genetic sequence was detected in 72 per cent of the Cultus cutthroat trout.

“This raises the questions: Is ISA virus impacting Cultus sockeye and other BC wild salmon populations? And at what cost to Canadians?” asked the report authors in a news release.

They say the findings are the first published evidence that ISAV, related to the influenza virus, is present in B.C. fish.

Federal government attempts to restore Cultus sockeye through fishing bans, enhancement and habitat restoration over several decades have been unsuccessful.

“The potential that viruses such as ISAV are contributing to widespread decline in sockeye salmon populations cannot be taken lightly,” states co-author Dr. Rick Routledge.

What’s needed is more sensitive screening tool.

Routledge told The Progress he isn’t sure why the Cultus Lake fish samples in particular had such high concentrations of the variant strain. It could have to do with their migratory routes.

“But I am hoping and am optimistic that the new federal government will take this matter seriously and encourage their scientists to pursue it with vigour,” said the researcher.

When ISAV was found in Chile in Atlantic salmon eggs, there was no effort to contain it. In 2007, it spread rapidly, causing $2 billion in damages and outbreaks continue. Unlike in Chile, B.C.’s wild salmon are an economic driver, adding billions of dollars to the economy through tourism, commercial and sports fishing.

So an outbreak would have “severe consequences” for B.C. as well as the Northwestern United States and Alaska.

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. But the hope is they will be able to test Atlantic salmon.

“This was a difficult strain of ISAV to detect, because of a small mutation,” says co-author Alexandra Morton, an independent researcher. “It is easy to see how it was missed, but we have cracked its code.”

Not everyone agrees with the study results. A salmon farm rep, along with B.C. government’s top fish expert, are taking issue with many aspects of the findings.

The Kibenge paper suggests the discovery of a variant of ISAV means the virus was confirmed in B.C. and may pose a risk to wild stocks like the Cultus Lake sockeye.

But critics have serious questions about the report and are refuting the claims by pointing out the virus can be present without causing any illness in fish.

They also questioned both the lab results and the scientific methodology.

The study by Dr. M. Kibenge and other researchers, including Morton, and  Routledge, posits that a new European strain of infectious salmon anemia virus (ISAV) was found.

“For over four years Ms. Morton has been reporting positive PCR tests for ISAV from BC samples, none of these results have been confirmed by the CFIA using OIEA standards,” said Jeremy Dunn, executive director of BC Salmon Farmers Association.

“We have great concerns about the methodology, and the ethics of the researchers involved given their history of reporting false positives with respect to ISA. None of the results reported in this paper have been confirmed by an outside laboratory.”

Farm-raised salmon in B.C. “are healthy and have never shown signs of sickness from ISA,” Dunn added in a statement sent to The Progress.

“This report claims to find an ISA sequence, but the researchers admit they were unable to verify it using necessary, globally standard follow-up tests.”

The variant strain may have been found but it was not confirmed by an outside lab, said Dr. Gary Marty in a written critique of the paper, being circulated by the salmon farming group.

Marty is a fish pathologist at Ministry of Agriculture, and he stated that he is “confident” the alleged test results pose no threat to either wild or farmed salmon.

“Lack of confirmation of results by an outside laboratory decreases my confidence in the results,” wrote Dr. Marty. “(The study by) Kibenge et al. (2016) did not provide information that their results were tested or confirmed by any outside laboratory.”

He also raised the spectre of false positives or sample contamination.

If the virus were truly present, it would have been detected in government samples already, “at least as often as Dr. Kibenge’s laboratory,” said Marty.

There would have been evidence before now, he said.

“Our veterinary virologist, Dr. Tomy Joseph, assures me that a single mutation in the probe sequence would not significantly affect our ability to detect levels of virus that might be causing disease.”

The Virology Journal is a peer-reviewed scientific publication from BioMed Central, a leading academic open access publisher in the areas of biology, medicine and health. More on the Kibenge study:  http://discoverynewvariantisav.typepad.com/my-blog/

For details on CFIA surveillance: http://www.inspection.gc.ca/animals/aquatic-animals/diseases/reportable/isa/epidemiological-evaluation-farmed-salmon/eng/1410060765809/1410060766512