COLUMBIA, S.C. (WCBD) – The South Carolina Department of Natural Resources (SCDNR) on Friday announced that the first cases of whirling disease have been discovered in trout populations sampled in the upstate.

SCDNR detected the disease, which is caused by the microscopic parasite Myxobulus cerebralis, in four streams across Pickens and Greenville counties.

The disease is not harmful to humans, but “has caused high trout mortalities in hatchery systems and in wild trout,” according to SCDNR chief of freshwater fisheries, Ross Self.

Trout infected with the disease suffer cartilage and skeletal damage, which causes them to swim in a “whirling” motion.

However, Self said that the disease “has not been observed to cause the classic disease symptoms here or seen to cause observable population declines.”

He explained that “it appears rare that this pathogen manifests as full-on whirling disease” in South Carolina’s environment.

To prevent exacerbating spread of the disease, SCDNR is reminding anglers not to “stock or remove trout around [or] between bodies of water, or release or dispose of them anywhere other than the location where they were caught.” All equipment should also be thoroughly disinfected and dried before reuse.