ARCHIVED - Salmon Disease Surveillance in British Columbia - Backgrounder

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The Canadian Food Inspection Agency (CFIA) is launching a salmon disease surveillance initiative in British Columbia.

In order to get a more complete picture of the health profile of the salmon populations in BC, the initiative will focus on three diseases: infectious haematopoietic necrosis, infectious pancreatic necrosis and infectious salmon anaemia.

The CFIA will lead the surveillance with support from Fisheries and Oceans Canada (DFO), the Province of British Columbia and industry. Sample collection is scheduled to begin in the spring of 2012.

In accordance with international reporting requirements, the CFIA will notify the World Organisation for Animal Health (OIE) of any confirmed positive finding in either farmed or wild fish. Test results will also be updated monthly on the CFIA’s website.

Diseases of concern

In Canada, infectious haematopoietic necrosis, infectious pancreatic necrosis and infectious salmon anaemia are “federally reportable diseases.” This means all suspected or confirmed cases must be immediately reported to the CFIA.

All three diseases are highly contagious and can cause mortality in wild and aquaculture salmon.

Infectious haematopoietic necrosis is known to exist in certain species and populations of wild finfish in BC. The surveillance initiative will determine its presence in certain species and populations of wild finfish in BC. Infectious pancreatic necrosis and infectious salmon anaemia have not been confirmed in BC.

Wild salmon disease surveillance

Approximately 5000 wild salmon will be collected per year for a minimum of two years, starting in the spring of 2012. Sample collection will begin as the salmon arrive at the selected points of collection in BC.

If one of the three diseases is confirmed in wild salmon, the CFIA may do the following:

  • identify exposed fish farms or other exposed wild fish populations to better define distribution
  • increase surveillance in wild salmon populations
  • place movement controls on harvested wild salmon
  • conduct an epidemiological investigation to determine possible sources and risk pathways

The specific disease response measures taken would depend on a number of factors, including the strain of the virus and the location in which it was detected. All testing, as well as any activities undertaken to respond to confirmed cases of disease, will be directed by science, international guidelines and national animal health requirements.

Farmed salmon disease surveillance

For farmed salmon, the CFIA is evaluating ongoing, industry-led testing programs. This may include inspection of aquaculture facilities, a review of documentation for testing, and, where required, animal sampling and testing. Once this evaluation is complete, future farmed salmon disease surveillance requirements will be determined and adjusted, if warranted.

The CFIA recently conducted a preliminary review of industry-led testing programs and found that there has been a significant level of testing for viral diseases in farmed fish over the last 10 years.

If one of the three diseases is confirmed in farmed salmon, the CFIA may do the following, depending on the specific circumstances involved:

  • implement quarantines on affected facilities
  • conduct further testing as required
  • launch an investigation to determine the source of the disease
  • require the humane destruction and disposal of infected fish
  • oversee cleaning and disinfecting at affected facilities

Test methods

Testing will be conducted in a DFO or CFIA-approved laboratory using internationally accepted testing protocols.

Generally fish samples will be screened using a test method called polymerase chain reaction (PCR). This test seeks to detect small portions of genetic material that match a virus’ genetic fingerprint. The PCR test is highly sensitive, and can sometimes produce false positive results. Therefore, positive results obtained at this stage require further confirmatory testing.
Confirmatory testing involves isolating the virus using cell culture. This process allows the virus to multiply as it would in a host fish. Confirmatory testing also involves conventional PCR testing, which matches larger and different portions of detected viral genes to the unique genetic fingerprint of known aquatic viruses.

Case definition

The CFIA’s definition of what constitutes a suspected versus a confirmed case of an aquatic animal disease is different for each of the three diseases of concern.

For example, for infectious salmon anaemia, the CFIA considers the virus to be suspected when

  • a non-CFIA approved laboratory reports a positive finding for the virus, or
  • the CFIA is notified of finfish showing clinical signs, or post-mortem lesions suggestive of the virus.

In order for infectious salmon anaemia to be confirmed, the virus must be isolated and identified by a National Aquatic Animal Health Laboratory System laboratory.

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