During routine fish health tests May 14, Mainstream Canada’s Dixon Bay farm tested positive for the IHN (Infectious Haematopoietic Necrosis) virus, the Campbell River-based company announced Tuesday.
Third-party lab PCR test results have shown the presence of the virus. Sequencing has confirmed the presence of IHN virus in these fish.
The farm site has been isolated and is currently being prepared for depopulation, if deemed necessary upon completion of the investigation. The company is following strict protocols to limit the spread of the virus. The protocols are part of Mainstream Canada’s fish health management plan as well as an industry viral disease management plan.
The Canadian Food Inspection Agency (CFIA) has been notified and is investigating the finding. Fisheries and Oceans Canada’s National Laboratory is conducting confirmatory testing.
“We are very concerned about this fish health event and are taking every step to make sure it is contained and any risks minimized,” said Fernando Villarroel, Mainstream Canada’s managing director. “This shows our disease monitoring programs work. We were able to quickly detect IHN while in its early stages and react decisively. Early detection is crucial to minimizing the risk in any fish health situation.”
The IHN virus is naturally carried by Pacific salmon, trout and herring. Studies show wild Pacific salmon have a natural resistance to the virus and very rarely suffer ill effects from it.
However, the virus causes Infectious Haematopoietic Necrosis disease in farmed Atlantic salmon. Since Atlantic salmon are not native to the Pacific coast, they have not had hundreds of years to develop a natural immunity to the virus, like their Pacific cousins. The disease can cause high degrees of mortalities on Atlantic salmon farms if not quickly managed and contained.
“This is the first diagnosis of IHN among farmed Atlantic salmon in BC since 2003. Although IHN kills up to 100 per cent of exposed Atlantic salmon, wild salmon in marine waters are very resistant to IHNV infection,” said Gary Marty, fish pathologist for the BC Animal Health Centre.
A lab study (Traxler et al, 1993) demonstrated this resistance under controlled laboratory exposure conditions. 25 virus-free sockeye salmon were added to a tank with 10 IHNV-injected Atlantic salmon. After 37 days, only one of the 25 sockeye salmon died, and the viral load in that fish was low.
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