The Wildlife and Freshwater Fisheries Division of the SC Department of Natural Resources, in conjunction with the Southeastern Fish Disease Cooperative at Auburn University, has documented the presence of whirling disease for the first time in four recently sampled streams in Pickens and Greenville counties.
This represents the first positive diagnosis of the whirling disease pathogen in South Carolina trout streams.
First detected in the United States in 1958, whirling disease is present in more than 20 states, including North Carolina and Georgia. Trout whirling can cause 90% or more mortality in young rainbow trout and can have serious impacts on wild and hatchery trout populations. The disease is caused by the microscopic parasite Myxobulus cerebralis, which damages the cartilage and skeletal tissue of trout, causing diseased fish to swim in a “swirling” motion.
“Although whirling disease is not harmful to humans, this disease has caused high trout mortalities in hatchery systems and in wild trout, particularly in western streams” , said Ross Self, chief of freshwater fisheries of the Department of Natural Resources (SCDNR) of SC. “There is no practical way to eliminate this pathogen. While the pathogen is now documented in South Carolina, it’s good news that it has not been observed to cause the classic symptoms of the disease here or to cause observable declines in the population. It seems rare for this pathogen to show up as a full swirl disease in southern Appalachian freestone streams like we have in South Carolina.
A recent fish health inspection at Walhalla State Fish Hatchery in Oconee County came back negative for whirling disease and other new exotic pathogens.
The SCDNR has conducted surveillance for exotic trout pathogens in wild trout and hatchery populations in Walhalla State for decades. Much of this work has been conducted in partnership with the US Fish and Wildlife Service‘s Wild Fish Health Project, operated out of their Fish Disease Laboratory in Warm Springs, Ga. Since 2015, the SCDNR has increased surveillance for whirling and other exotic pathogens in trout due to recent documented outbreaks of whirling trout and two species of parasitic gill lice in neighboring states. At this time, no parasitic gill lice have been documented in South Carolina trout.
SCDNR fisheries biologists, said themselves, will take additional samples of trout for disease analysis during the upcoming summer/fall 2022 survey season.
Anglers are reminded NOT to store or move trout between bodies of water or release or discard them anywhere other than where they were caught. Anglers are also reminded to always sanitize waders and thoroughly clean all equipment before leaving a fishing area. Thoroughly dry the equipment in the sun if possible before using it again. If anglers go directly to other waters, they are asked to clean their equipment with a 10% bleach solution or use other equipment.
For more information on whirlwind, visit the United States Department of Agriculture website at https://www.invasivespeciesinfo.gov/aquatic/pathogens-and-diseases/whirling-disease.