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For More Information:  
Daniel Sutherland, Professor of Fish Parasitology, University of
Wisconsin-La Crosse, (608) 785-6982
Phil Moy, Fisheries Specialist, UW Sea Grant Institute, (920) 683-4697
Stephen Wittman, Assistant Director for Communications, UW Sea Grant
Institute, (608) 263-5371


MADISON, Wis. (10/30/00) -- Rainbow and brook trout in western Wisconsin
streams could fall prey to a deadly disease that devastated the prized fish
in Colorado and Montana in the early 1990s, according to a recent University
of Wisconsin Sea Grant study.

Known as whirling disease, the disorder is caused by a parasite called
Myxobolus cerebralis, according to Daniel Sutherland, a fish parasitologist
at UW-La Crosse who conducted the research.  The parasite infects and
deforms the heads and spines of trout, turns their tails black, and leaves
them able to swim only in circles, Sutherland said.  During his three-year
study, Sutherland found that streams in western Wisconsin could support
large numbers of the myxobolus parasite if it were introduced into those

The parasite has been found in Michigan, but in numbers too low to cause
whirling disease, Sutherland said.  However, Myxobolus cerebralis is likely
to thrive in western Wisconsin streams because they harbor large numbers of
an aquatic worm called Tubifex tubifex, he said.  This worm is an essential
host to the myxobolus parasite during part of its life cycle, Sutherland
said.  Therefore, streams with large numbers of tubifex worms could support
large numbers of parasites and possibly engender whirling disease in trout
that live there, he said.

In his study, Sutherland measured populations of Tubifex tubifex in
Wisconsin's tributaries of the Mississippi and Lake Michigan.  He found
relatively small populations of the worm in eastern Wisconsin streams.
Those few worms could support only small numbers of the myxobolus
parasite--probably too few to cause an outbreak of whirling disease, he

In the streams of western Wisconsin, however, Sutherland found "astronomical
figures of the tubificid worm, higher than we've seen anywhere else.  If the
parasite gets into western Wisconsin trout waters, I think we have the
potential for an outbreak of whirling disease," he said.

Trout fishers can do much to reduce the chances of whirling disease taking
hold in Wisconsin, Sutherland said.  After filleting trout, they should bury
the carcass, dispose of it in the garbage, or incinerate it--all methods
that will prevent the potentially infected bone and cartilage of the head
and spine from being returned to the stream.  

Fishers should also be careful not to transport mud or water, both of which
can harbor the parasite, from infected areas in Michigan back to Wisconsin.
Waders and boats should be rinsed off thoroughly, and live wells should be
cleaned and dried before transporting the boat.

Finally, trout should never be used as bait fish, Sutherland said.


Created in 1966, Sea Grant is a national network of 29 university-based
programs of research, outreach, and education dedicated to the protection
and sustainable use of the United States' coastal, ocean, and Great Lakes
resources.  The National Sea Grant Network is a partnership of participating
coastal states, private industry, and the National Sea Grant College
Program, National Oceanic & Atmospheric Administration, U.S. Department of

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