Step 1

Microscopic spores are found on the river bottom.

Step 1

Bottom-dwelling tubifex worms eat the spores.

Step 3

Bottom-dwelling tubifex worms eat the spores.

Step 4

Inside the tubifex worm, the spore changes form and becomes a Triactinomyxon (TAM).

Step 5

The TAMs are released from the tubifex worm and into the water.

Step 6

Trout become infected when the tiny TAMs cling to the fish's body and work their way into the fish's nervous system.

Step 7

Once inside the fish, the TAM changes form again and moves into the fish's cartilage near the head where it develops into a mature spore.

Step 8

After several weeks, infected fish may exhibit a "whirling" behavior, spinal deformities and black tails.

Step 9

When the infected fish dies or is eaten by a predator, the spores in its body are released into the water and the cycle starts over.

Step 10

People are saddened when they learn that whirling disease has been found in their favorite river. However, everyone is hopeful that a solution will be found.