Rainbow trout afflicted with whirling disease


North Carolina’s first cases of disorder

FOSCOE – Whirling disease, a disorder affecting trout, has been confirmed in rainbow trout collected from Watauga River near Foscoe in Watauga County — the first occurrence of the disease in North Carolina.

Whirling disease affects fish in the trout and salmon family with rainbow and brook trout, two species found in North Carolina waters, being the most susceptible. The disease, caused by the microscopic parasite Myxobolus cerebralis, damages cartilage and skeletal tissue in a fish, causing it to swim in a whirling motion. While often fatal to juvenile fish, the disease does not infect humans or pets, and eating an infected fish is not known to cause any harmful effects.

The parasite that causes whirling disease was first discovered in Pennsylvania in 1956. Since then, whirling disease has been confirmed in other states, with varying degrees of severity. In some states, whirling disease has been observed in isolated cases and has had little impact while in other states, such as Montana and Colorado, the impacts on trout populations have been more pronounced.

Although the infected trout were collected from a section of the Watauga River well upstream of public trout stocking locations, the N.C. Wildlife Resources Commission has proactively suspended stocking fish raised at its three trout hatcheries until it can confirm that hatchery trout are free of the disease. As one of many precautionary measures, staff is collecting fish from Commission trout hatcheries and sending them to the Fish Disease Laboratory at Auburn University for testing.

“So far, we have no indications that trout at any of our hatcheries are infected with whirling disease, but we are being extra cautious and having fish tested before we resume stockings,” said Doug Besler, the Commission’s regional fisheries supervisor for the mountain region. “We hope to have test results back within the next few weeks and once we rule out whirling disease infection at our production facilities, we will resume planned trout stocking operations.”

Commission staff will also collect trout from the Watauga River and tributary streams to test for whirling disease and to determine its distribution in the watershed. In addition, Commission staff is working closely with N.C. Department of Agriculture and Consumer Services and N.C. State University to sample commercial aquaculture operations in the area where the infected trout were found.

The Commission encourages the public to help prevent the spread of the parasite that causes whirling disease by cleaning and drying equipment, clothing, or anything else that comes into contact with water. In addition, no one should move live fish or aquatic wildlife from one body of water to another without first obtaining a permit from the Commission. Anglers are asked to contact the Commission if they observe deformities, strange swimming behaviors, or other signs of disease in trout.

For a list of frequently asked questions on whirling disease, to learn more about whirling disease and its effects on trout, and to report signs of disease in trout visit the Commission’s dedicated webpage, www.ncwildlife.org/whirlingdisease. The page will be updated as test results become available.

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North Carolina’s first cases of disorder
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