"Whirling disease" is a disease of salmonids, the family of fish that includes trout, salmon, and whitefish. Whirling disease is caused by a microscopic parasite known as Myxobolus cerebralis, and gets its name from the abnormal whirling or tail-chasing behavior exhibited by some infected fish. Other symptoms include a blackened tail and head or spinal deformities. However, fish may be carriers of the parasite without having any visible signs. Most species of salmonids are susceptible to whirling disease infection and, particularly in young fish, the disease can cause high mortality rates.

Read this Fact Sheet or check out these reports by Trout Unlimited:

Whirling Disease in the United States: A Summary of Progress in Research and Management (1999).
Whirling Disease in the United States: Overview and Guidance for Research and Management (1996).

Visit the links on the right to learn more about whirling disease.



Microscopic triactinomyxons (TAMs) are the form of the whirling disease parasite that is infective to fish. Research in the field is a key component for the Whirling Disease Initiative. Protection of fishing opportunities is very important to the Initiative.