Whirling Disease

The Elk River is in danger of becoming BC’s entry point for whirling disease; this could have significant impacts on our local trout and hence the $2.7 M/year fishing industry. 

Invasive species are nothing new. Since the transport revolution, resilient plants and animals have followed global transport routes wreaking havoc on local ecosystems as they go. Rats were stowaways on sea voyages, seeds of invasive plants follow hikers on their shoes, and plenty of species–such as cane toads, mongooses, and even cats– were introduced as a pest control attempt only to become a pest themselves. Aquatic species are often accidental travellers, and are transported via ballast water, by growing on ship hulls, or by attaching to equipment.

Such is the case for a small aquatic parasite called Myxobolus cerebralis, which causes whirling disease in juvenile trout. Commonly transferred through infected fish restocking facilities, this parasite also spreads via recreational water users. A super hardy spore stage allows it to survive in dry environments and it can travel via boat ballast, in mud, or attach to hulls, waders, and fishing equipment. Once present, eradication is virtually impossible. 

Currently, the BC Government encourages river users to diligently Clean, Drain, and Dry all of their equipment before transferring it between streams. Removing any vegetation, cleaning mud, and waiting until all equipment is fully dry is an essential step especially when travelling between different water bodies.

Originally from Europe, whirling disease was first detected in North America in 1958, and was reported in Canada’s Banff National Park for the first time in 2016. 

After an intensive monitoring program, it was found that many of Alberta’s southern water bodies had whirling disease infected fish, including the Crowsnest watershed. Anglers travelling between Albertan waters and the Elk River therefore have a high chance of inadvertently introducing the parasite into British Columbia and beyond. 

The culprit M. cerebralis has a creepy yet fascinating biology comprising two life stages: the “TAM” (triactinomyxon) stage and the “spore” stage. A TAM has three spikes and floats in the water until it attaches to fish skin and injects its cells into the fish. The cells then travel along the nervous system until they reach the soft, undeveloped cartilage of juvenile fish. There, they feed on the cartilage and develop from the TAM stage into the spore stage. Intense infection causes an inflammatory response which kinks the fish spine and causes a dark discolouration; two signs of potential whirling disease infection. While adult fish–whose cartilage already developed into bone–are fairly resilient to whirling disease, for young fish infection is a death sentence. 

In addition to trout, M. Cerebralis needs a second host: the worm Tubifex tubifex. Within the worm, the spore stage develops back into the TAM stage so the cycle can repeat. In 2022, the Elk River Alliance has started a Whirling Disease Education and Monitoring program which not only aims to familiarise the local community on the risks and vectors of whirling disease spread, but also to monitor streams for Tubifex tubifex presence. Our hope is that understanding the presence of this essential host will allow us to determine the risk our watershed faces of allowing M. cerebralis to spread. So far, we’ve detected Tubifex tubifex in five streams: Boivin Creek, Elk River at Hosmer, Morrissey Creek, Lizard Creek, and Michel Creek.

Adhering to the “Clean, Drain, Dry” mantra is a great way to slow the spread of other invasive species as well, such as Zebra Mussels and Eurasian Milfoil. To learn more about whirling disease and the ERA program, go to elkriveralliance.ca/whirling.