What is Whirling Disease and what fish are affected?
Whirling disease is a parasitic infection caused by the microscopic parasite, Myxobolus cerebralis. The disease is named for the characteristic swimming behavior that results as the parasite multiplies in the head and spinal cartilage of the infected fish. It attacks juvenile trout and salmon, but does not infect warm water species. All species of trout and salmon may be susceptible to whirling disease, and other members of the trout and salmon family, such as mountain whitefish are also at risk. Rainbow trout and cutthroat trout appear to be more susceptible than other trout species. Brown trout become infected with the parasite, but they appear to have an immunity to the infection and have not been as greatly impacted as rainbow trout. Studies in Montana and at the University of California-Davis have demonstrated that grayling and bull trout are very resistant to infection.
How is whirling disease transmitted?
Whirling disease is transmitted by infected fish and fish parts. It may also be transmitted by birds and it is possible fishermen could carry the disease on fishing equipment. However, live infected fish are the main vector for the spread of the disease.
What is being done to fight whirling disease?
The Whirling Disease Foundation coordinates a national effort to combat whirling disease. Each year, the Whirling Disease Symposium brings scientists and mangers together to discuss the latest whirling disease research and plan future research priorities. Over 200 university, state agency and federal scientists are now conducting research on the problem.
How can I prevent the spread of the disease?
First and foremost, do not transport live fish or carry fish or fish parts from one drainage to another. If fishing known whirling disease infected waters, care should be taken to rinse all mud and debris from equipment and wading gear, and drain water from boats before leaving the infected drainage.
Is there hope?
Yes. Just a few years ago, whirling disease had infected many of our finest trout streams, causing precipitous population declines in some. Little was known about the disease parasite, Myxobolus cerebralis, and its Tubifex tubifex worm host. Today, it's true that total eradication of the parasite is not likely, but recent studies by the nation's finest researchers point out real possibilities for management and control. For example:
-A new commercially available water-filtering device that uses ultraviolet light can kill the WD parasite in hatchery water sources and help control its spread.
Studies indicate that disease hotspots exist in rivers, and that some hotspots may no bigger than, say, a banquet table or two. Knowing this, it may be possible to manage around or even clean up some of these hotspots, and increase the survival rate for nearby spawning trout.
-A Montana study successfully imprinted wild trout eggs with a cold-water spawning temperature which may help the fry emerge earlier, thus avoiding the period of heavy infection.
-In Colorado, a test study is underway to filter the parasite from a heavily infected tributary, which may lower the mainstem infection.
What can I do to help?
Learn more about whirling disease. Do not transport live fish or fish parts. Take proper care of fishing equipment when moving among drainages. Provide financial support for the efforts of the Whirling Disease Foundation to combat the disease and fund whirling disease research.
Can humans get whirling disease?
No, the parasite can't infect humans.
