Whirling Disease

The first documented case of trout whirling disease in Canada was detected in August 2016 at Johnson Lake, in Banff National Park. The parasite responsible for the disease, Myxobolus cerebralis, is native to Europe, and was introduced to North America in Pennsylvania in 1956. It has subsequently spread westward across the continent. Surveillance is currently being conducted to determine if it has spread further into Canadian waters.

While not a risk to human health, this organism primarily impacts rainbow (steelhead) and cutthroat trout under the age of four months. In a worst-case scenario, the infected fish can die. After a fish reaches four months, it becomes fairly resistant to this microscopic parasite. The various species of anadromous salmon appear to be more resistant to M. cerebralis than these trout species. However, what is vitally important to anglers and recreationists is that – due to the parasite’s miniscule size and complex life stages – whirling disease is extremely difficult to contain and impossible to eradicate from water bodies once they are impacted.

Whirling disease is generally transmitted to other water bodies through gear and equipment used for fishing, swimming, paddling, boating, or the movement of contaminated fish (live or dead) or fish parts. With many visitors travelling between Alberta and B.C., here are important precautions that you can take to help stop the spread of this disease if you’re going to be out on the water:

  • There are two recommended methods for cleaning:
    1) using very hot water (close to 90° C) on non-plastic items or gear that won't melt or deform, or
    2) a solution of one part chlorine (household bleach) to 32 parts water.
    Preferably, conduct your cleaning at the site before leaving. Be sure to thoroughly clean all sand, mud, and plant material from your boat, trailer, clothing, boots, and any other equipment used in your water activity.
  • When cleaning at home, use a solution of one part chlorine (household bleach) to 32 parts water. Do not dispose of the chlorine solution used in the decontamination process into municipal storm drains or water systems; instead, spread it over a nearby lawn or garden. Note, at the suggested dilution level, the solution will not harm lawns or gardens.
  • Allow at least 24 hours of drying time in sunlight before entering new waters.
  • Remove all water from equipment like waders, boots, live wells, and bilges before transferring.
  • Do not transfer live fish from one water body to another. It is illegal to do so in B.C.
  • Do not use fish as bait.
  • Dispose of fish, entrails, and other waste in municipal garbage, not in the water body.

Infected fish can display several physical signs, including a blackened tail, spinal deformities, and erratic swimming (in a whirling pattern). It’s important to note that these physical signs are often not evident, and no outward indication of infection is common. That is why it is critical that you follow the best practices above in all situations. Whirling disease can be deadly – and in other regions of North America, notably Montana and Colorado, it has had devastating effects on wild trout fisheries.

Already detected in a number of lakes in neighbouring Alberta, the Province has been vigilant in preventing the spread of this microbe into B.C.

To create a continuity across Western Canada, biologists in our province are using sampling methods for Myxobolus cerebralis that are aligned with those used by Government of Alberta and Parks Canada. Samples are being tested in the labs using Polymerase Chain Reaction methods. Last year, samples of over 880 fish from six sites in the Columbia Basin (Elk River, Premier Lake, Lower St. Mary River, Koocanusa tributaries, the Kootenay River near Creston, and the Columbia River near Castlegar and Trail) were tested. Luckily, all samples tested negative for whirling disease.

Still, we must be alert. For 2018, the Province has formulated a multi-faceted defense to prevent the spread of whirling disease into B.C. Based on similar procedures created to prevent the spread of other invasive species (like zebra and quagga mussels), the Early Detection Rapid Response Plan (EDRR) provides detailed direction on the decisions and actions required to address new incursions anywhere in B.C. Effective decontamination procedures have been developed to prevent the spread of the disease by human vectors. Monitoring and sampling of high-risk water bodies, focussing on areas with substantial human activity, will continue in and around the Columbia Basin.

If you see fish with any symptoms of Whirling Disease, contact Front Counter BC Toll free at 1-877-855-3222 or email FrontCounterBC@gov.bc.ca

Author: Stephanie Whyte; Whirling Disease Coordinator Funded by Habitat Conservation Trust Foundation, The Province of BC, & The Freshwater Fisheries Society of BC.
Photo Credit: Daniel Krenz & Stephanie Whyte