The TAM attaches to the fish’s skin and injects the parasite into the fish’s body. Afterward, the TAM is released from the worm into the water column where it floats until it comes into contact with a susceptible fish. Inside the worm, the myxospore changes form and become a TAM. The myxospore is a small, round spore that infects the Tubifex worm.

Two of these are infective spore forms, called the myxospore and the triactinomyxon (TAM). The fish host is a salmonid fish.Īs many as 10,000 Tubifex tubifex worms can be found in one square yard of a muddy river bottom.ĭuring its life cycle, the parasite takes several physical forms. This worm is very small (about 1/2-inch in length) and is very common and widespread around the world. The worm host of the parasite is called Tubifex tubifex. Without these two hosts, the parasite cannot complete its life cycle and will die without multiplying. The whirling disease parasite has a two-host life cycle, alternating between a small worm and a fish. There is no known cure for fish infected with the whirling disease parasite. In severe infections, whirling disease can cause death. Other physical signs of the disease include darkened tail, twisted spine, or deformed head.

This causes the fish to swim erratically (whirl) and have difficulty feeding and avoiding predators. The parasite penetrates the head and spinal cartilage of salmonid fish where it multiplies very rapidly, putting pressure on the organ of equilibrium. The disease is caused by an invasive parasite known as Myxobolus cerebralis.

Whirling disease is a disease of salmonid fish, the family of fish that includes trout, salmon, and whitefish. Illustration by Randy Bright Provided by Montana Fish, Wildlife, and Parks

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