Whirling Disease (Myxobolus cerebralis)

Volume 1, Issue 2
December 1999
Updated November 2003

Whirling Disease is an infectious disease that affects trout. This disease has not been found in Maine’s trout, but as long as anglers travel elsewhere and then fish in Maine, it will remain a threat. Whirling Disease has been found in 18 of the 50 states.

The following summary is from Introduction to Fish Health Management, edited by Becky A. Lasee, Second Edition.

Whirling disease is a chronic parasitic infection of cultured and wild salmonids caused by the myxosporean parasite Myxobolus cerabralis (syn. Myxosoma cerebralis). Myxosoma cerebralis has a specific appetite for trout skeleton cartilage. Infection can result in head deformities, axial skeleton deformities, deformed tails, and neural damage.

infected trout

Fig. 2. Black tail seen in rainbow trout infected by Myxobolus cerebralis.
Images from P. Goddard Utah Fish and Game.

Infected fish sometimes have black curved tails. These deformities can persist throughout the fish’s life. Fish with deformities or whirling behavior indicate whirling disease, they, however, are not conclusive. Nutritional deficiencies, fungal infections, and exposure to chemical contaminants may produce similar clinical signs. A definitive diagnosis requires identification of the infecting spores from the fish’s cartilage. Two hosts are required for the parasite to live: a fish and an oligochaete worm, Tubifex. Two separate phases of spore formation occur, one in each host. The spores produced in fish are released into the water when the infected fish dies or is consumed by a predator. These myxosporean-type spores are then ingested by the Tubifex worm. Young fish are infected when they eat spores or tubifex worms. Some fish may display abnormal tail chasing, whirling, during feeding or when alarmed. These changes are believed to be due to nervous system damage and loss of cartilage around the organs of balance.

fish jaw

Fig. 1. Jaw deformity resulting from juvenile infection by Myxobolus cerebralis.

If you observe a fish with the symptoms of whirling disease, contact a game warden, or call the Maine Department of Inland Fisheries & Wildlife, Fish Health Lab at 1-207-287-2813.

Control Measures

*Clean all equipment of mud (boats, trailers, waders, boots, float tubes and fins before leaving any out-of–state waters. Thoroughly dry equipment in the sun, before using it again. If you are traveling directly to Maine waters, clean your equipment with a 1% bleach solution to sanitize it or use another set of equipment.

*Don’t release live baitfish into water.

*Don’t dispose of fish heads, skeletons or entrails in any body of water. Fish parts should be disposed of in the garbage, by deep burying or by total burning.

Special points of interest:

No Whirling Disease exists in Maine.

Myxobolus spores & tubifex worms can be inadvertently transported on fishing equipment.

There is no cure for whirling disease in fish.

Whirling Disease originated in Europe and spread to the USA around 1955.

Other information is at http:/

Whirling Disease links

Montana Water Center--Whirling Disease Initiative


WD Foundation