What fish species are affected?
Most salmonids (salmon, trout and whitefish) are susceptible to infection. Some rainbow and cutthroat trout appear to be more susceptible than other trout species. Brown trout become infected with the parasite, but do not usually exhibit signs of the clinical disease. Studies in Montana and at the University of California-Davis have demonstrated that grayling and bull trout are very resistant to infection. Other salmonids, such as mountain whitefish, are also at risk. How is whirling disease transmitted? Whirling disease is usually transmitted by infected fish and fish parts that carry the parasite. It may also be transmitted by birds and it is possible fishermen could carry the disease on fishing equipment. Regardless of whether a fish shows signs of the disease, infected fish release the parasite into the environment when they die, contaminating the drainage. Myxobolus cerebralis spores can live through drought and freezing for up to 30 years. Spores infect its alternate host, the wo
