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Whirling Disease: What it is and how to keep it out of the Athabasca Watershed
Watershed Issues | Invasive Species, Prevention, and Whirling Disease | May 2019

Whirling Disease (Myxobolus cerebralis) is a recent threat to aquatic species in Southern Alberta that has been making its way up to the Athabasca Watershed.  Whirling Disease was first observed in the United States in the 1950s4.  In Canada, the first detection of Whirling Disease was in Johnson Lake, Banff National Park, 20164, however it is unknown where the parasite first established in Alberta5. Whirling disease has been confirmed in four major watersheds in Alberta by Alberta Environment and Parks (AEP), it remains undetected in the Athabasca and Peace1.  

What is Whirling Disease? 

Whirling Disease is a microscopic parasite that infects tubifex worms (Tubifex tubifex)3.  The organism has a complex lifecycle that requires a Salmonid (Trout, Salmon, Charr, Grayling, and Whitefish) and Tubifex worms as hosts1.  The parasite invades cartilage and impairs the nervous system of Salmonids1. Whirling Disease affected waters can cause up to 90% mortalities in native and non-native Trout, and Mountain White fish1.  

The parasite that causes Whirling Disease is considered an aquatic invasive species by the Alberta Invasive Species Council since it is established outside of its natural range and causes significant harm to the environment, the economy, and society2

Photo: Calgary Herald 

What species can be infected by Whirling Disease? 

Whirling Disease is not a risk to human health or other mammal species, but several species of Salmonids are at risk of being affected1.  Currently, it is not known to impact other organisms1.  

Species susceptible to Whirling Disease include:  

  • Rainbow trout (Oncorhynchus mykiss
  • Cutthroat trout (Oncorhynchus clarkii
  • Brook trout (Salvenlinus fontinalis)  
  • Mountain whitefish (Prosopium williamsoni)
  • Coho salmon (Oncorhynchus kisutch
  • Sockeye salmon (Oncorhynchus nerka
  • Chinook salmon (Oncorhynchus tshawytcha
  • Atlantic salmon (Salmo salar)
  • Brown trout (Salmo trutta)
  • Bull trout (Salvelinus confluentus)

The severity of Whirling Disease depends on the age and size of salmonid host. Young and small fish are most vulnerable1. Rainbow Trout, Brown Trout, Mountain Whitefish, and Brook Trout species have been infected more than other species of Salmonids1.  

What are the signs of Whirling Disease? 

Not all infected Salmonids show signs of Whirling Disease3. Affected Salmonids can be seen swimming in a tail chasing, whirling swimming pattern1. They can appear with skeletal deformities of the body or head. Their tail can also appear dark or even black1.  

Photo: State of Colorado 

How is Whirling Disease spread? 

Whirling disease is not spread between Salmonids3.  It is spread through Salmonids and tubifex worms3. Infectious spores can also be transmitted to other water bodies through various ways1.   

People can spread Whirling Disease by moving: 

  • Infected live or dead Salmonids from one water body to another (illegal in Alberta) 
  • Infected worms 
  • Pet fish and/or aquarium to surface water
  • Pets from one waterbody to another
  • Contaminated equipment
  • Contaminated water
  • Contaminated mud and sand 
  • Contaminated plant material 
  • Contaminated fish and fish parts
  • Contaminated equipment
  • Contaminated bathing suits and waders
Photo: Alberta Government

See full image here.

Where is Whirling Disease found? 

Whirling Disease has been detected in 4 major watersheds within Alberta: Bow River, North Saskatchewan River, Oldman River, and Red Deer River1.  No new cases of whirling disease have been detected in Alberta since March 20186; fish collected by the GoA from the Athabasca watershed were tested in 2019 and confirmed negative1. Whirling disease has been detected in B.C., in the Columbia Watershed7. While whirling disease has been detected in these watersheds, it does not mean that the parasite is found in all waterways in these systems.

How is Whirling Disease diagnosed? 

Whirling Disease requires laboratory testing since not all infected Salmonids show signs of the disease3.  

How is Whirling Disease treated? 

There are currently no treatment options available for Whirling Disease3

What is currently being done to prevent the spread of Whirling Disease? 

AEP created the Whirling Disease Program to protect Alberta’s Salmonid Species after the initial discovery of the parasite1.  AEP also formed a response team that includes biologist, hydrologists and emergency response personnel to ensure a quick response when the disease has been detected1.  The Whirling Disease Program has since been incorporated into the Aquatic Invasive Species program.

A new Whirling Disease laboratory has been established in Vegreville, Alberta1.  It is exclusively dedicated to testing for and preventing the spread of Whirling Disease with additional staff for education and mitigation efforts1.  The University of Alberta is also working to develop non-lethal testing methods for the Whirling Disease parasite1.  

What are the socio-economic impacts of Whirling Disease? 

Whirling Disease directly affects anglers in Alberta by reduced angling opportunities since public and private stocked waters may experience closures. Over 300,000 angling licenses are sold annually to Albertans. The recreational angling market value in Alberta is approximately $500 million.

What can I do to prevent the spread of Whirling Disease? 

First, be aware of the water bodies that are contaminated with Whirling Disease. Second, know the signs that show Whirling Disease is present in a Salmonid species3. Third, if you think a Salmonid has Whirling Disease immediately notify the Canadian Food Inspection Agency (CFIA) (587) 230-22003

When entering, leaving, and living near a waterbody please be sure to: 

  • Use fish cleaning stations 
  • Dispose of dead fish in garbage 
  • Never dispose of fish, or fish parts, in your kitchen garburator
  • Never use live fish as bait 
  • Never dispose of aquarium or pet fish in a natural water body
  • Never move fish from one waterbody to another waterbody
  • Never introduce fish from another country to a Canadian waterbody
  • Worms and leeches as bait should also be avoided
  • Clean your watercraft
  • Clean your equipment
  • Clean footwear, waders, and swim gear
  • Clean and brush pets after contact with waterbody
  • Remove all standing water
  • Drain water from watercraft and equipment onto dry land before leaving shore
  • Dry watercraft and equipment completely between trips (minimum 24 hours of drying time)
  • Never clean boat and equipment near storm drains, ditches or waterways  

For more details from the Alberta Government on cleaning, draining and drying your watercraft and water equipment, see:

Clean, Drain, Dry Your Boat 


1 Alberta Environment and Parks. Whirling Disease Program Report. Edmonton : Alberta Environment and Parks, 2017. 

2 Alberta Invasive Species Council. Fisheries Act (Alberta). Alberta Invasive Species Council. [Online] 2019. [Cited: May 15, 2019.] https://abinvasives.ca/invasive-species/fact-sheets/fisheries-act/. 

3 Canada Food Inspection Agency. Whirling Disease – Fact Sheet. Government of Canada. [Online] September 12, 2016. http://www.inspection.gc.ca/animals/aquatic-animals/diseases/reportable/whirling-disease/fact-sheet/eng/1336686597267/1336686806593. 

4 Government of Alberta. Whirling Disease. Government of Alberta. [Online] 2019. https://www.alberta.ca/whirling-disease.aspx?utm_source=redirector. 

5 Government of Alberta. Whirling Disease in Alberta: Misunderstandings Debunked. Government of Alberta. [Online] 2024. https://open.alberta.ca/dataset/56221860-1a8c-4a0a-88a6-65e5a4aac696/resource/7b4b93fc-e652-4d2b-a721-f4dec368a36c/download/aep-whirling-disease-misunderstandings-2020-01.pdf

6 Government of Canada. Locations infected with whirling disease. Government of Canada. [Online] 2024. https://inspection.canada.ca/en/animal-health/aquatic-animals/diseases/reportable-diseases/whirling-disease/locations-infected

7 Government of Canada. Notice to Industry – Update on Zoning for Whirling Disease- British Columbia and Columbia River Watershed. Government of Canada. [Online] 2024. https://inspection.canada.ca/en/animal-health/aquatic-animals/diseases/reportable-diseases/whirling-disease/update-zoning-whirling-disease

Initially written May 2019; updated in May 2024