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
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
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
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.
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.
* Organizes scientific meetings devoted to research progress.
* Maintains a Web site that provides updates on research, literature and
* Develops outreach materials for educators and the public.
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
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
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
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
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
"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
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
1. Never move live fish from one body of water to another.
If you are interested in learning more about whirling disease, visit
these Web sites:
2. Don't dispose of entrails or heads in any stream or other body of
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
Whirling Disease Foundation at www.whirling-disease.org
Montana Water Center at http:water.montana.edu or
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.