Whirling disease is a parasitic condition affecting fish, primarily rainbow trout. It is present in many Colorado rivers and in a number of state hatcheries.
Once the disease parasite is established in the wild, it can persist indefinitely, depending on environmental conditions.
Efforts to reduce the parasite in hatcheries are proving successful.
The Colorado Parks and Wildlife has developed strict policies and regulations to help control and prevent the spread of the disease in Colorado.
To find out how it affects fish and what you can do to help, see Whirling Disease.