What kinds of fish are susceptible to whirling disease?
All species of trout and salmon can be infected with the parasite, but not all species will develop whirling disease. There is a wide range in susceptibility to the disease. Rainbow trout and cutthroat trout appear to be the most susceptible of trout species. Brown trout can become infected with the parasite and may carry the disease, but they are much more resistant to the disease and have not been as greatly impacted as rainbow trout. A lot of research has been conducted to determine the risk of whirling disease to each species of trout, salmon, grayling and whitefish. Scientists have also found that the age of the fish when first exposed to the parasite is very important. Very young fish are highly susceptible, but after a fish reaches four months old it is fairly resistant to whirling disease.
