Whirling Disease is a disease affecting juvenile salmonid fish, including trout and whitefish. It is caused by a microscopic parasite, Myxobolus cerebralis, which infects fish through their skin.
Although there is no risk to human health, the parasite can be lethal in rainbow (including steelhead) and cutthroat trout under four months of age. In infected waters, whirling disease may cause high mortality in fish populations depending on the age and size of the salmonid host (trout, salmon, whitefish); juvenile fish are most susceptible to infection.
The severity of an outbreak is difficult to predict due to various interacting factors between habitat and environmental conditions. However, in extreme circumstances, localized population collapses of more than 90% have been observed in some streams in the Western United States.
As you may have heard, Whirling Disease is now in the Eastern part of the Columbia Shuswap Region. On October 27, 2023, Parks Canada closed all water access in Yoho and Kootenay national parks following the discovery of a suspected case of whirling disease in Emerald Lake, British Columbia.
This was the first detection of whirling disease in the province. Further testing detected whirling disease in the Kicking Horse River, Wapta Lake, Finn Creek, Monarch Creek and the confluence of the Emerald and Kicking Horse rivers. These results were confirmed by the Canadian Food Inspection Agency testing in December 2023.
To reduce the risk of further spread of whirling disease and protect vulnerable species at risk, all waterbodies in Yoho and Kootenay national parks are closed to watercraft and angling until March 31, 2025. These restrictions are designed to help protect fish species vulnerable to whirling disease, including several trout species and Kokanee salmon.
This closure will also provide Parks Canada with an opportunity to conduct further sampling and monitoring actions, which will inform future management actions.
Protecting lakes and rivers is a collective responsibility. We all have an important role to play.
We want to highlight a few key points: – Whirling Disease is federally regulated through the Canadian Food Inspection Agency – The Province, Parks Canada and CFIA are all coordinating on monitoring and next steps, and we are staying apprised of how we can support regionally – Invasive Species Council of BC (ISCBC) has a webinar presentation from Parks Canada on whirling disease on May 28th 12-1 pm PST.
