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Alaska Department of Fish and Game Information on British Columbia Report on Infectious Salmon Anemia Virus (ISAv)

November 14 Update:

New test results indicate there are no confirmed cases of Infectious Salmon Anemia (ISA) in British Columbia (B.C.) wild or farmed salmon. These test results were based on analysis conducted by the Canadian Food Inspection Agency (CFIA) in close collaboration with Fisheries and Oceans Canada (DFO), the Province of British Columbia and the Atlantic Veterinary College (AVC).

Alaska/U.S. Response to the ISAv Incident:

  • Alaska Department of Fish and Game (ADF&G) pathology labs will incorporate Infectious Salmon Anemia virus (ISAv) testing into statewide routine annual surveillance testing of adult and juvenile salmonids. Confirmation of any suspected ISAv would include Polymerase Chain Reaction (PCR) testing, currently done for other salmonid pathogens in Alaska.
  • The U.S. Department of Agriculture – Animal and Plant Health Inspection Service is working on a surveillance plan for ISAv and has been in contact with Washington and Alaska fish pathologists to help in development of the plan
  • Washington and Alaska senators have introduced an amendment to a bill which was passed the U.S. Senate to prioritize federal agency involvement in surveillance of ISAv in the Pacific Northwest.

Background:

In October, heart tissues from two of 48 Rivers Inlet sockeye salmon smolts tested PCR-positive for low levels of the European strain of ISAv at the Atlantic Veterinary College of Prince Edward Island (PEI), a reference lab for Infectious Salmon Anemia virus (ISAv). There was no evidence of ISAv disease in these fish when collected. They were reportedly normal in appearance and behavior. Gill tissues from theses same fish were also tested at the University of Bergen in Norway. One of the previously positive samples indicated weak evidence of ISAv at the outer detection limits of the polymerase chain reaction (PCR) test for ISAv. However, this one weak positive could not be replicated in 32 repeated assays. Therefore, the original Rivers Inlet positive results for ISAv from the PEI lab could not be confirmed and are inconclusive.

ISAv is an enveloped single-stranded Ribonucleic acid (RNA) orthomyxovirus belonging to the influenza virus group. The virus was first detected in Norway in 1984 and has caused disease and severe losses in Atlantic salmonin Europe. Subsequently, the virus has resulted in devastating losses of Atlantic salmon in various locations including the maritime coast of North America (New Brunswick and Maine in 1996 and 2001, respectively) and Chile in 2007.

Important considerations regarding the B.C. ISAv:

  • Research on ISAv indicates that risk to Alaska’s salmon stocks is low. Pacific salmon are relatively resistant to infection and disease from ISAv, which is a viral disease of Atlantic salmon. The susceptibility of sockeye salmon to ISAv has not been experimentally tested. Other Pacific salmon including Chinook, coho, and chum salmon as well as steelhead trout do not develop disease when injected with the Norwegian strain of ISAv, but may become infected and carry the virus for varying periods of time. However, injection is an unnatural route of infection that would not occur in nature.
  • Other strains of ISAv in North America are not pathogenic in Atlantic salmon. However, these viruses can mutate into more virulent strains, therefore we have cause for some concern.
  • Atlantic herring reportedly carry the virus, but do not become diseased. This forage species could act as a reservoir and source of the virus.
  • Although live Atlantic salmon are prohibited from importation into Alaska, there is some straying of escapees from B.C. farms, which could provide an avenue for the virus to enter Alaska waters. However, ISAv testing by PCR of Atlantic salmon (4,726 tests) from B.C. farms by the Canadian government over the last 8 years, including the past three months, has been negative for the virus. Therefore, the risk of virus transmission from such escapees is very low.
  • ISAv does not transmit to humans and is not a human health or food safety issue.

Additional Information: