Whirling Disease

Whirling disease is caused by an invasive, microscopic parasite known as Myxobolus cerebralis. The parasite has two hosts during its life cycle, a worm (Tubifex tubifex) and a salmonid fish. The parasitic spores first infect the Tubifex worm and after developing, the parasite is released into the water. The parasite floats along the water column until it encounters a susceptible fish. Once attached to the fish’s skin, the parasite enters the body and travels through the nervous system feeding on cartilage and begins to multiply. Damage to the cartilage and skeletal tissue causes the fish to swim erratically (whirling). In 2015, the disease was confirmed in rainbow trout collected from a North Carolina river. 

For more information, visit our Aquatic Nuisance Species page.

Whirling disease only affects fish in the trout and salmon family (Salmonoid). Rainbow and brook trout are the most susceptible species to this disease. 

Physical signs of whirling disease include darkened tail, twisted spine and/or deformed head.

Whirling disease can alter feeding habits and the ability to avoid predators. Due to undeveloped skeletal tissue, juvenile fish are more vulnerable to whirling disease than adults. The severity of infection decreases with increased age in fish. There is no known cure for whirling disease in fish.

The disease does not affect humans or pets. Eating an infected fish is not known to cause any harmful effects. Though this disease is not a risk to human health, take precautions to clean all fishing equipment properly, do not transport live fish from one water body to another and dispose of fish parts appropriately. This will help reduce the spread of the disease to other bodies of water.