What is ceratomyxosis?

Ceratomyxosis is a disease that affects salmon and trout. It is caused by the protozoan Ceratomyxa shasta, which belongs to the class Myxosporea.

What species of finfish can be infected with ceratomyxosis?

Each species of finfish may have several common names, but only one common name is listed.

Species susceptible to ceratomyxosis that occur in the natural environment in Canada:

  • Oncorhynchus clarkii (cutthroat trout)
  • Oncorhynchus gorbuscha (pink salmon)
  • Oncorhynchus keta (chum salmon)
  • Oncorhynchus kisutch (coho salmon)
  • Oncorhynchus mykiss (rainbow trout)
  • Oncorhynchus nerka (sockeye salmon)
  • Oncorhynchus tshawytscha (chinook salmon)
  • Salmo salar (Atlantic salmon)

Is ceratomyxosis a risk to human health?

No. The causal agent of ceratomyxosis is not a risk to human health.

What are the signs of ceratomyxosis?

Ceratomyxosis causes death in

  • previously infected adult finfish returning to spawn
  • young finfish in hatcheries
  • young finfish that have been transferred from freshwater to seawater
  • finfish which spend their entire lifecycle in freshwater

Affected finfish may exhibit any of the following signs:

  • behaviour
    • swimming slowly
    • loss of appetite
  • appearance
    • weight loss
    • dark skin colour
    • an enlarged belly that is filled with fluid
    • pockets of pus or other types of fluid in the liver, kidney, spleen or muscle
    • protruding, reddened vent
    • bulging eyes
    • bleeding in the intestines in adult fish
    • areas of bleeding on the internal organs

Is ceratomyxosis found in Canada?

Yes. In Canada, ceratomyxosis has been found in wild finfish in the Pacific Ocean watershed of British Columbia.

How is ceratomyxosis spread?

Ceratomyxosis is not spread directly between finfish. The protozoan requires a freshwater worm (Manayunkia speciosa) to complete its life cycle. The parasite is spread between the finfish and the worm through contact with water contaminated with spores that have been released by infected finfish and worms.

People can spread ceratomyxosis by moving any of the following:

  • infected live or dead finfish,
  • infected worms, or
  • contaminated water.

How is ceratomyxosis diagnosed?

Diagnosing ceratomyxosis requires laboratory testing. Not all infected finfish show signs of disease.

How is ceratomyxosis treated?

There are no treatment options currently available for ceratomyxosis.

What measures can be taken to prevent the introduction and spread of ceratomyxosis?

If you frequently handle or work with finfish, be aware of the clinical signs of ceratomyxosis.

Do not import live infected finfish into Canada.

  • An import permit is required from the Canadian Food Inspection Agency (CFIA) for certain species of finfish as of December 2011.
  • People bringing finfish into Canada should check other federal, provincial, and/or territorial requirements before entering the country.

Do not introduce live finfish from another country into the natural waters of Canada.

  • People releasing finfish into the natural waters or in rearing facilities within Canada should check if federal or provincial and/or territorial permits are required.

If you frequently handle or work with finfish, be aware of where Ceratomyxa shasta occurs in your area.

  • A federal, provincial and/or territorial permit or licence may be required to relocate finfish within Canada.

Do not use finfish that were bought in a grocery store as bait for catching finfish or other aquatic animals.

When cleaning and gutting finfish, dispose of all finfish waste in your municipal garbage.

The CFIA recommends that you do not visit Canadian aquaculture sites, zoos or aquariums for 14 days if you have travelled to another country and

  • visited an aquaculture site, or
  • had contact with wild finfish.

Wash and disinfect the footwear you wore to the site or when you had contact with wild finfish. Also wash your clothing thoroughly and dry it at a high temperature.

What is done to protect Canadian aquatic animals from ceratomyxosis?

Ceratomyxosis is a reportable disease in Canada. This means that anyone who owns or works with aquatic animals, who knows of or suspects ceratomyxosis in their fish, is required by law to notify the CFIA.

If ceratomyxosis is found outside of known infected areas in Canada, the CFIA would control its spread by implementing disease response activities. These may include

  • controlling movements of infected animals that people own or work with
  • humanely destroying infected animals
  • cleaning and disinfecting

The control measures chosen would depend on the situation.

What do I do if I think finfish that I am raising or keeping have ceratomyxosis?

If you suspect a finfish that you are raising or keeping may have ceratomyxosis, you are required under the Health of Animals Act to immediately notify the CFIA.

How do I get more information?

For more information about reportable diseases, visit the Aquatic Animal Health page, contact your local CFIA Animal Health Office, or your CFIA Area office:

  • Atlantic: 506-777-3939
  • Quebec: 514-283-8888
  • Ontario: 226-217-8555
  • West: 587-230-2200
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