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The waterborne parasite Myxobolus cerebralis commonly known as Whirling Disease may not kill fish but can severely deformed their features. The name comes from the common characteristic of the fish to chase it's tail. The parasite requires two hosts to survive. One host is the aquatic tubifex worm and with trout/ salmon species being the second hosts. Thousands of Triactinomyxons (TAMs) spores are released into the water when an infected fish dies or in the excrement of a predator fish that has eaten an infected fish. The spores settles to the bottom where the spore is injested by a tubifex worm. The spores can survive in sediments for 20 to 30 years while surviving large temperature variations including being dried out or frozen. Inside the tubiflex worm the spore develops into the triactinomyxon stage where it then is released into the water. After entering the water the triactinomyxon stage must infect a host fish within 3-4 days. Fish can also get infected by eating the tubiflex worm. Warm water species of fish are not affected by Whirling Disease.

This parasite can affect most trout and salmon species including white fish. According to the Alaska DF&G Arctic Grayling and Lake trout are resistant to the parasite. Our brown trout are descended from brown trout brought from Europe where Whirling Disease probably originated. Thus brown trout have a natural resistance to the parasite but some do become deformed and discolored from the parasite. Rainbow trout are exceptionally susceptible to the parasite. Though adult fish can carry the parasite without any visible signs of infection, juvenile fish are very susceptible to deformity and coloration changes. The tail area of an infected fish can turn black. see picture Juvenile fish can easily become heavily affected by the parasite because it attacks the soft cartilage of the fish before it hardens into bone. Few reach maturity when they are severely deformed it is hard for them to feed or avoid predators. Since many of the young don't mature in good health, natural in-river reproduction of rainbow trout has declined dramatically in many of our prime river fishing habitat. See this slide. Once the fish is 4 to 5 inches long the cartilage has formed into bone and it is no longer susceptible to the deforming affects. Mature fish will continue to live a normal life span even though they may carry the parasite without any deformity. Currently there is not practical way to protect wild trout populations. Many rainbow trout populations in our state waters are maintained by stocking more mature trout rather than through natural reproduction or the stocking of juvenile fish.

The WD spores, which can survive for 20 to 30 years in a river/lake bottom, can be transported by animals, fowl, and humans. They can withstand extremes in temperature and dehydration. Spores can survive in dried mud on a boot for up to one year. The State of Utah says that their infected waters are all within quick access to a road. The spores can be killed with strong disinfectants like bleach (5000 PPM of chlorine for 10 minutes ). The Alaska Department of Fish and Game recommends disinfecting wading equipment with a 1 part bleach to 9 parts water. The whirling Disease Initiative website says that QACs (quaternary ammonium compounds) will kill both life forms of whirling disease. See our wading equipment sanitizing page for procedures.

Native Fish protection:
Many of our native cutthroat populations are in high mountain rivers and lakes which mostly have not been infested with Whirling Disease. The DOW website says "As of July 2005, empirical evidence indicates that only one Rio Grande cutthroat trout population and one Colorado River cutthroat trout population may be at risk of extirpation due to infection by M. cerebralis." It is important that anyone fishing in the high mountain streams and lakes containing Rio Grande, Colorado, and Greenback Cutthroat trout sanitize their wading equipment before going. It are these bodies of water that are going to insure continued existance of these fish. Also take note that recent research postively shows that wading equipment can transfer both stages of Whirling Disease from one body of water to another. Across the nation a number of state wildlife agencies are recommending not to use felt soles because they can easily transport parasites and invasive species like the NZMS and are hard to thoroughly sanitize. When you harvest fish for a meal do not put fish heads or entrails in the stream as they can contain thousands of WD spores that can be transferred to the water or to other fish. Burn or bury they them. At home don't put the entrails down the garbage disposal as the spores can survive water treatment plants. Disposal in land fills is the way to go.

Hatcheries:
Eleven of 16 state trout hatcheries were confirmed to have whirling disease back in 1998. Six of those facilities have since been modified and sanitized so that they are now whirling disease free. Fish from contaminated hatcheries are stocked only in waters already contaminated or distroyed. None are shipped out of state. The state has been doing a number of research studies to understand WD environmental factors better, remediate hot spots and monitor current stream contamination. see this page

Whirling disease does not infect humans. People cannot contract the disease from eating or handling infected fish.

West Denver Trout Unlimited