Deadly virus appears in Washington state salmon farm – Pacific Fishing

Pacific Fishing, 25th May 2012

A virus has infected a Bainbridge Island salmon farm, forcing the owners to begin culling and destroying infected fish.

It’s the same disease – infectious hematopoietic necrosis virus, or IHNV – that caused a British Columbia salmon farm to destroy 560,000 fish last week. The fish ended up in a composting facility.

Another British Columbia salmon farm announced this week that it
had voluntarily quarantined itself because the disease was found in its stock.

Alan Cook is vice president for aquaculture at Icicle Seafoods,
which owns American Gold Seafoods, the operator of the Bainbridge Island salmon farm at Orchard Rocks.

“There is no human health implication,” he said. “The virus is
endemic. Wild fish have it. The disease came from wild fish to our fish, not the other way around.”

Cook said the path of the disease can be proved by DNA analysis.
Hugh Mitchell, a Seattle area veterinarian who specializes in fish, agrees. The disease “is endemic. It’s common. It’s part of the natural ecosystem.”

At the Orchard Rocks farm, diseased fish are being culled. Fish
large enough for the market are being butchered and sold, Cook said. Smaller fish are destroyed.

He declined to say how many fish were in the farm.Once the stocks are gone, the farm will be fallow for three months.
Nets will be removed and disinfected, Cook said.

The largest financial hit for Icicle will come from lost production.

“More than anything else, it’s the cost of the loss of livestock,” Cook said.

There has been a salmon farm for 30 years at that Bainbridge Island location. Never before has it been hit by IHNV, Cook said.

However, the disease was reported in salmon farms in British
Columbia about 10 years ago, Mitchell said.

The disease is part of the natural ecosystem in the North Pacific. Wild salmon species here have built some resistance to the virus. Healthy wild fish can withstand the infection.

However, Atlantic salmon used in farming have no resistance to
the disease, Mitchell said. They are made even more susceptible to disease because they live in close confinement.

“Farmed fish are way more susceptible to wild diseases,” Mitchell said.

And why did the disease made another appearance this year and
not others?

“No one knows,” Mitchell said.

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