Infectious Salmon Anaemia - Fact Sheet

Infectious salmon anaemia (ISA) is a finfish disease caused by a virus that belongs to a family of viruses called Orthomyxoviridae. ISA is a reportable disease in Canada. This means that anyone who suspects ISA in finfish that they own or work with is required by law to notify the Canadian Food Inspection Agency (CFIA).

What species of finfish can be infected with ISA?

Species known to be susceptible to ISA include:

  • Oncorhynchus mykiss (rainbow trout)
  • Salmo salar (Atlantic salmon)
  • Salmo trutta (brown trout)

Species that may be susceptible include:

  • Salvelinus alpinus (Arctic char)
  • Clupea harengus (Atlantic herring)

Is ISA a risk to human health?

No. There is no evidence that ISA can be transmitted to humans.

Has ISA been found in Canada?

Yes. ISA was first detected in the Atlantic area in 1996. It has been reported in New Brunswick, Nova Scotia, Prince Edward Island and Newfoundland.

ISA has not been found in the Pacific Ocean watershed or the Pacific Ocean off British Columbia.

For more information of confirmed cases of ISA in Canada, visit Federally Reportable Aquatic Animal Diseases in Canada.

What are the signs of ISA?

ISA outbreaks are most common in susceptible farmed finfish reared in seawater. The disease has not been seen at the embryo stage, but can affect the fish at any life stage after hatching. It tends to be a slow moving disease so the death rate may initially be low and increase over time (weeks to months). Depending on the strain of virus, outbreaks of ISA can cause death rates of up to 90 per cent in affected populations of finfish. On average, mortality on any given farm is 30 per cent.

Infected finfish may exhibit any of the following signs:

  • loss of appetite;
  • abnormal swimming patterns (slow swimming, swimming slowly at the surface);
  • fish gasping at the surface;
  • grey gills;
  • swollen abdomen;
  • areas of bleeding that may be present along the belly and sides of the fish;
  • dark and swollen kidney, liver and spleen;
  • areas of pinpoint bleeding in the fatty tissue surrounding organs;
  • areas of bleeding in the pyloric cecae, intestines and liver;
  • pale heart; and
  • bloody fluid in the abdominal cavity and around the heart.

What is required to confirm a diagnosis of ISA?

When ISA is suspected, the CFIA launches an investigation to collect all relevant information, such as signs of illness in the fish and previous disease outbreaks in the area. At the same time, samples are collected and sent for laboratory testing using validated protocols at one of Canada's three National Aquatic Animal Health Laboratories.

How is ISA treated?

There are no treatment options currently available for ISA. There is a vaccine available in Canada to prevent the disease.

How is ISA spread?

ISA may be spread between finfish by contact with:

  • excretions and/or secretions from infected finfish; or
  • water contaminated with the virus.

People can spread ISA by moving:

  • infected live or dead finfish;
  • contaminated equipment; or
  • contaminated water.

What measures can be taken to prevent the spread of ISA?

Anyone who frequently handles or works with farmed or wild finfish should:

  • be aware of ISA occurrences in the local geographic area;
  • be aware of the signs of ISA;
  • not use finfish bought in a grocery store as bait for catching finfish or other aquatic animals; and
  • dispose of all waste from cleaning and gutting finfish in municipal garbage.

Owners of aquaculture facilities are encouraged to implement biosecurity practices that will minimize the introduction and spread of ISA between production facilities. Finfish handlers must apply and comply with all federal, provincial and/or territorial permits or licences that may be required for the purpose of disease control prior to import into or relocation of finfish within Canada.

How does the CFIA respond if ISA was suspected in an aquaculture facility?

If ISA is suspected, the CFIA places movement controls on the facility to control movement of fish, vessels and/or vehicles, and equipment on and off the site. In these circumstances, finfish, vessels, vehicles and equipment could only be moved into or out of the facility with CFIA approval.

If ISA is confirmed, the CFIA controls its spread by carrying out disease response activities. These activities vary depending on the situation and could include:

  • controlling the movements of infected animals;
  • overseeing the humane destruction of infected animals;
  • verification of cleaning and disinfection activities; and
  • requiring the facility to be left empty for a period of time (fallow period) prior to restocking.

Additional information

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