Know Whirling disease is a parasitic condition affecting fish, primarily rainbow trout. Other species of trout and salmon are affected to lesser degrees. Warm-water fish such as bass, walleye and catfish are not affected. Whirling disease does not infect humans. People cannot contract the disease from eating or handling infected fish.
Young fish are most susceptible because the parasite attacks their soft cartilage.
Clinical signs of infection include skeletal deformities or whirling motions during swimming. Once trout reach three to four inches in length, cartilage forms into bone and fish are no longer susceptible. Larger infected fish generally don't die but are carriers of the disease. In the vast majority of cases, infected adult fish show no signs of the disease, exhibit regular behavior and go on to live normal lifespans. As yet, there is no practical cure to treat wild trout infected with the disease.