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NW Fishletter #297, December 14, 2011

[1] 2002 Research May Have Found Signs Of ISA Virus In Wild Salmon

Results from a Canadian researcher who claimed to have found traces of the ISA virus in wild salmon nearly 10 years ago have finally seen the light of day. Molly Kibenge's draft report was leaked to anti-fish farm groups last month, after the scientist failed to get permission from a fellow author to present those results for publication.

If true, the results of Kibenge's post-doctoral research could mean that wild salmon populations in Alaska and British Columbia have harbored a non-pathogenic strain of the ISA virus for at least the last decade.

The ISA virus has devastated farmed stocks of Atlantic salmon in Norway, Chile and eastern Canada, but has not been detected in B.C. farmed fish, even after thousands of tests. Wild fish in other parts of the world may carry the virus, but do not seem to be adversely affected by it, at least in its present forms.

Department of Fisheries and Oceans scientists at the Pacific Biological Station in Nanaimo, B.C., where the work was performed, did not support the conclusion that the ISA virus had been detected, because all attempts to isolate the virus into cell culture failed, according to an email response to Kibenge from Simon Jones, one of Kibenge's co-authors of the draft paper. The email was leaked along with the draft paper.

That means the results did not comply with the strict definition of ISAV infection, Jones said in the Nov. 4 email. The definition "requires either the isolation and identification of the virus into cell culture from two independent samples taken on two separate occasions, or the isolation and identification of ISAV in cell culture plus RT-PCR [reverse transcription--polymerase chain reaction] or serologic confirmation from tissue preparations. You may further recall that an independent laboratory was unable, on more than one occasion, to reproduce your RT-PCR results on the same samples," said Jones. "In my opinion, it will be very important to understand the disagreement in laboratory results and to better test the hypothesis of 'Asymptomatic ISAV' before moving towards publication."

But the groups that circulated the information the day before it ran as a front-page story in The Seattle Times characterized it as a "DFO cover-up."

"The DFO has a split mandate, one that includes the promotion of aquaculture and which has interfered with their responsibility to protect wild salmon," said Kurt Beardslee, executive director of the Duvall, Wash.-based Wild Fish Conservancy, in a Nov. 30 statement. "Unfortunately, we have a similar situation in the U.S. NOAA also has a pro-aquaculture division that works at odds with the scientists studying salmon conservation. Until this split mandate is removed, oversight cannot be left solely to government."

Dr. Todd Sandell, a disease ecologist at the WFC, said "it is a near certainty that ISAV will also be found in Washington state." His group said it began collecting samples for testing from the Skagit River in November, but so far, state and federal agencies have not taken action.

Canadian government officials said in a Nov. 8 joint-agency press conference that they were unable to confirm the presence of the ISA virus in samples of wild B.C. sockeye smolts that had shown signs of the virus in previous tests in a different lab, where both Kibenge and her husband now work. Her husband, Fred Kibenge, had conducted the PCR testing that led to the results announced at an Oct. 18 press conference at Simon Fraser University.

On Dec. 2, the Canadian Food Inspection Agency announced it had completed testing on all the original samples--along with nearly 300 more that were partially or totally degraded--and was unable to confirm the presence of the virus in any of them. All attempts at growing cell cultures and amplifying and sequencing genetic material also failed, the agency reported.

The CFIA also noted that years ago, it was unable to find traces of the ISA virus in any of the samples in which Molly Kibenge had found signs of the virus. "We did a thorough investigation into her findings," said DFO scientist Stephen Stephens. "We sent her samples to our laboratory in Moncton (New Brunswick), and they did multiple tests, replicates of the test, to try and find the ISA virus that she had reported on, and we were unable to reproduce any of her results."

Testing for confirmation of the original results has been going on since mid-October, in collaboration with Fisheries and Oceans Canada, the province of British Columbia, and the Atlantic Veterinary College at the University of Prince Edward Island, where the original testing was conducted.

The results from the newly unearthed draft paper found that 28 percent of the juvenile chinook samples and 17 percent of the juvenile pink salmon (from Vancouver Island and southeast Alaska) showed signs of ISAV. All samples from spawning sockeye (Cultus Lake in the lower Fraser watershed) and one cultured Atlantic salmon showed signs, and other parts of genomic sequences for the virus were found in some chinook, more than 100 different salmon in all.

According to the paper, "these results lead us to conclude that an asymptomatic form of ISA occurs among some species of wild Pacific salmon in the north Pacific." No signs of the virus were found in chum or coho samples.

USGS fish disease expert James Winton, who is based in Seattle, told NW Fishletter that he was not aware of the 2002 research results until the paper was leaked. He said the results have not confirmed the possibility that wild fish may have picked up ISA from salmon farms, nor whether it is virulent or not.

Winton said the ISA virus exists in wild populations in other parts of the world, but the wild strain doesn't really grow in cell cultures--which, until now, has been one of the official tests for proving its presence. But he said the international body that governs testing protocols for these fish viruses--the OIE, or World Organization for Animal Health--is revisiting the accepted testing procedures for ISA.

Winton said that by calling other results "false positives," the DFO may be misleading, since the testing it has done may be compromised because scientists are looking for something they haven't seen before. "The sequence data is more compelling," he said, referring to Molly Kibenge's results.

Winton said a wild strain of ISAV may have been present on the West Coast long before the fish farms showed up. Anti-fish farm advocates have pointed to the 2004 importation into B.C. of salmon eggs from a North Atlantic hatchery as a probable source of the virus.

Other viruses that have shown up in Northwest salmon hatcheries were originally thought to be exotic pathogens. VHS is one of them, and adversely affected coho. In 1989, strong control measures were taken to control the disease, but later it was discovered to be endemic throughout the Pacific region, common in herring, pilchard and cod.

B.C. salmon farms were also plagued by the IHN virus, which was found originally in native sockeye populations. Wild stocks had been able to adapt to it, while the farmed Atlantic salmon had not.

Meanwhile, Fred Kibenge, an internationally known expert in the ISA virus himself and one of the draft paper's co-authors, said its results were being sent to the Canadian Food Inspection Agency "as part of their ongoing investigation."

In a Nov. 14 email response to DFO scientist Simon Jones, Kibenge said his lab was getting ready to take part in this process and would "disclose this work notwithstanding its age. I think that this historical data may also clarify some of the issues around recent ISAV testing in B.C."

The Cohen Commission that has been investigating the potential causes for the collapse of the 2009 Fraser sockeye run will convene a special two-day session Dec. 15-16 to hear evidence on the ISA virus in Canada.

The virus controversy has led the U.S. to begin development of a monitoring program on this side of the border. "These troubling reports reinforce the need for a coordinated, multinational strategy to control the spread of this virus threat," Sen. Maria Cantwell (D-Wash.) said in a statement. "American and Canadian scientists need to have access to all relevant research."

Cantwell, along with Lisa Murkowski (R-Alaska) and Mark Begich (D-Alaska), led an effort that just passed Congress, requiring the National Aquatic Animal Health Task Force (an existing partnership between USDA, USGS, NOAA and others) to report to Congress in six months on the research, interagency coordination, and responses necessary to deal with potential effects of the ISA virus.

The Canadians are also developing a surveillance program to look for signs of the virus in farmed and wild fish. They plan to sample wild fish between March and November of next year.

Virus expert Winton said if wild salmon do harbor a strain of the virus that is harmless to them, it could turn into a dangerous situation if farmed salmon picked it up. Crowded growing conditions can make mutations more likely to occur, and there is no telling how virulent a mutation is likely to be.

He said he was not very confident that trying to control the distribution and spread of the virus would be all that effective. "It may just be buying you some time," he said. -Bill Rudolph

The following links were mentioned in this story:

Molly Kibenge's draft report

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