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Part Seventy-three



Whirling Disease

By Dick Wesnick, Billings MT


Less than a decade ago, few people in Montana had ever heard of whirling disease, a lethal disease which has devastated wild trout fisheries throughout the United States.

Whirling disease is believed to have originated in Europe. In the United States, it was reported almost simultaneously in the late 1950s from hatcheries in Pennsylvania and Nevada.Since then it has spread to both coasts and has been found in 22 states. It has also been detected in Central Europe, Northeast Asia, New Zealand and South Africa.

Today, more than 200 scientists at universities and state and federal agencies across the nation are conducting research into whirling disease.

Whirling disease is caused by a parasite called Myxobolus cerebralis which infiltrates the head and spinal cartilage of fingerling trout where it multiplies rapidly, causing the fish to swim erratically and, in severe cases, die.

When an infected fish dies, millions of tiny indestructible Myxobolus cerebralis spores are released into the water where they can survive this 'dormant' form for up to 30 years. When the spores are ingested by tiny tubifex worms living in the river bottoms, the spore changes and is released from the worm in a highly infective form call Triactinomyxon, or 'Tam÷' for short.

Tams float freely in the water until they infect trout, causing spinal deformities and decreased ability to feed.

Whirling disease was considered such a serious threat to Montana's native fisheries that former Gov. Marc Racicot established a Governor's Task Force on Whirling Disease. The Task Force spent four years working with the state Department of Fish, Wildlife and Parks to develop coordinated plans for addressing the problem through research, education, public information and departmental policies.

It is, to be sure, a serious threat to native and wild trout which means it is also a serious threat to Montana tourism. But, as any trout fisherman will tell you, Montana has and will continue to have one of the finest trout fisheries in the world. And the Madison River continues to be a world class blue ribbon trout stream.

Whirling disease is not dangerous to humans or animals; it targets only salmonids - trout, salmon, char and steelhead. It also does not infect warm-water species such as bass or walleyes.

In the six years since whirling disease was first discovered in our state waters, Montana has become a world leader in that research through the efforts of the Whirling Disease Foundation in Bozeman, and the Wild Trout Lab at the Montana Water Center at Montana State University.

The Whirling Disease Foundation was founded in 1995 and began addressing the problem by supporting scientific research on a national scale.

The Foundation's mission is to ˘eliminate the threat of whirling disease to native and wild trout, char, salmon and steelhead populations through research and education.

Additionally, the Foundation:

    * Helps coordinate multi-institutional research protocols and plans.

    * Organizes scientific meetings devoted to research progress.

    * Maintains a Web site that provides updates on research, literature and activities.

    * Develops outreach materials for educators and the public.

The Foundation recently conducted its seventh annual National Whirling Disease Symposium, which this year was held in Salt Lake under the auspices of the Utah Division of Wildlife Resources.

To illustrate the seriousness of the problem, a press release issued following the symposium started this way:
"Whirling disease: It's considered a modern plague that is devastating trout throughout America."

Another agency that is working on the whirling disease problem is the Wild Trout Lab on the MSU campus. It is managed by the Montana Water Center and oversight is provided by a steering committee with representatives from the U.S. Fish and Wildlife Service, the Montana Department of Fish, Wildlife and Parks, the Montana Cooperative Fishery Unit, and the Whirling Disease Foundation.

The lab is uniquely suited for fish disease work because of its redundant water/wastewater purification system. Researchers can conduct studies on potentially dangerous organisms without the threat of release into the environment.

Whirling disease was unknown to Montana waters until it was in the Madison River in December of 1994. In the ensuing years, it destroyed an estimated 90 percent of the rainbow trout there.

Whirling disease has since been found in trout in more than 80 streams and rivers in Montana, and recently was discovered in Yellowstone Lake in Yellowstone National Park.

Since the very beginning, the leader in coordinating state research has been Dick Vincent of the Montana Department of Fish, Wildlife and Parks. Vincent said that progress is being made through research and study on rivers throughout the state.

He believes that two key elements to controlling the impact of whirling disease are water temperatures during the spawning period, and water flow rates.

Vincent suggests that rainbow trout, which are highly susceptible to whirling disease, could adapt to spawn earlier when water temperatures are colder, thus giving the young trout time to develop sooner and avoid the period when they are vulnerable.

In the Madison River, water flow rates can be influenced by water releases from the dam and by runoff, Vincent said.

"They are hatching from mid-June to mid-July. That period is the most vulnerable. If they flows are low, you tend to have high infection rates. In 1998 and '99 we had very high flows and infection rates were down. In '97, flows were low and the infection rate was high."

He believes that low flows tend to concentrate the Tams in the water while they are 'diluted' or disbursed during high flows, allowing rainbows to evade infection.

This could be a poor year, Vincent said, because of low flows. "We're going to explore that this year," he said.

Elsewhere in Montana, infection rates have been high, Vincent said. "2000 was the worst we've ever seen on Rock Creek," which is east of Missoula.

"The Big Blackfoot has intensified but it's still not a serious problem. It is still evident in the Missouri River system, and it has expanded into the Gallatin River basin.

"It is very widespread in Yellowstone Lake. We can't really say if it's damaging the fish population but 25 percent of the fish taken by gill nets are infected. They may be measuring survivors."

The infection of fish is also intensifying in the Yellowstone River basis above Livingston. From Mill Creek to the Shields, the disease is in its early stages.

It has not yet been found in Big Spring Creek or the Bighorn River in Montana, but it is evident in the Wind River in Wyoming which becomes the Bighorn around Thermopolis.

Whirling disease can be spread in several ways, and it can be spread by humans as well as birds.

According to the Whirling Disease Task Force's Web site (www.whirlingdisease.org), the most likely means of spreading the parasite is through the movement of live fish or parts of fish. A single fish can be infected with many thousands of spores, making an infected fish the most dangerous source of infection.

Birds are also suspected as a potential vector of whirling disease. University studies have shown that viable parasites can pass through the digestive tract of birds and still be infective to fish.

Here are some ways that you can help prevent the spread of whirling disease:

    1. Never move live fish from one body of water to another.

    2. Don't dispose of entrails or heads in any stream or other body of water.

    3. Don't discard entrails or heads of fish down a garbage disposal. Place them in the garbage for disposal into a landfill site.

    4. Wash the mud off your boat, trailer and other equipment before leaving the water where you've been fishing.

    5. Thoroughly wash and dry your boots and waders. If possible, dip or spray on a high concentrations of chlorine bleach. Make sure you thoroughly rinse the chlorine off your waders and other equipment after you disinfect them. Chlorine is a very strong chemical and can harm your equipment with prolonged exposure.

If you are interested in learning more about whirling disease, visit these Web sites:

Whirling Disease Foundation at www.whirling-disease.org

Montana Water Center at http:water.montana.edu or wwwrc@montana.edu

Whirling Disease Task Force at www.whirlingdisease.org

~ Dick Wesnick

Editor's Note: Dick Wesnick, of Billings, Mont., was a member of the Montana Governor's Task Force on Whirling Disease.


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