What is Whirling Disease?
Whirling Disease is a pathogen that affects Salmonid fish species (salmon, trout, and whitefish). In Alberta, species that may be infected include Cutthroat Trout, Brown Trout, Brook Trout, Bull Trout, Rainbow Trout, and Mountain Whitefish. Whirling Disease is caused by Myxobolus cerebralis, a parasite that has a two-host life cycle. The pathogen requires both a tube-worm host and a fish host. Tube-worms live in the sediment of waterbodies, and take up spores produced by the Whirling Disease pathogen. Within the tube-worm, the spores develop into a free-swimming form, which moves through the water column until it encounters a fish host. It travels into the cartilage where it produces spores, which are then released into the water.
Why is Whirling Disease a Problem?
Whirling Disease only affects fish at the juvenile stage. When Whirling Disease enters a fish host, it migrates into the cartilage and begins to grow. It feeds on the cartilage, resulting in skeletal deformities such as a twisted spine, deformed jaws, and misshapen heads. These deformities are very painful, and cause the fish to swim in a jerking, whirling pattern. Due to this altered swimming pattern and deformed jaw, an affected fish is unable to feed properly, and is more susceptible to predation. As a result, infected populations can see a 90% mortality rate among young fish.
Currently there is no cure for Whirling Disease. Once a water body is infected, there is no way to effectively eradicate the pathogen. The best defense again Whirling Disease is prevention.
Currently there is no cure for Whirling Disease. Once a water body is infected, there is no way to effectively eradicate the pathogen. The best defense again Whirling Disease is prevention.
What are the Symptoms of Whirling Disease?
Infected fish may not always show symptoms. Typical signs of Whirling Disease in juvenile fish:
- Twisted or bent spine
- Blackened tail
- Jaw deformities
- Shortened gill covering (operculum)
- Erratic swimming pattern
How is Whirling Disease Spread?
Whirling Disease is predominantly spread though the transport of infected fish or sediment that contains spores. Whirling Disease can be spread naturally through birds and mammals that eat fish, or through water currents that can move spores downstream. However, humans can greatly facilitate the spread of Whirling Disease through recreational activities such as fishing or boating. Infected fish, fish parts, or sediments that are inadvertently introduced into new watercourses can spread spores. Even sediments that may go unnoticed on boots, waders, or boats can have a big impact. Proper disinfection of clothing and equipment is necessary to prevent the spread of Whirling Disease. For effective disinfection procedures, click here.
Where is Whirling Disease in Alberta?
Whirling Disease was first detected in Alberta in August of 2016, in Johnson Lake, Banff National Park. It was the first case of Whirling Disease in Canada. The Bow, Oldman and Red Deer River watersheds have since been declared infected.
Is Whirling Disease Harmful to Humans?
Whirling Disease does not impact humans, birds, or wildlife. Humans can not contract Whirling Disease, and fish infected with Whirling Disease are safe to eat.
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