Where is whirling disease found?
The parasite that causes whirling disease (Myxobolus cerebralis) was introduced to North America from Europe, where it’s native. It was first discovered in the United States in Pennsylvania in 1956. Since then, it has been reported in numerous states and continues to spread. The presence of the parasite doesn’t always mean whirling disease will cause dramatic population losses. In a number of states, the parasite has been observed only in isolated cases and has had very little noticeable impact. However, the disease can be a serious problem in hatcheries, and in Montana and Colorado, severe impacts on wild trout populations have been documented. The whirling disease parasite’s range is expanding in the United States and the impacts vary from river to river. There is some distribution information available on this Web site. For more information, you may also call your local fish and wildlife agency.
