For More Information: Daniel Sutherland, Professor of Fish Parasitology, University ofWisconsin-La Crosse, (608) 785-6982Phil Moy, Fisheries Specialist, UW Sea Grant Institute, (920) 683-4697Stephen Wittman, Assistant Director for Communications, UW Sea GrantInstitute, (608) 263-5371
WISCONSIN TROUT VULNERABLE TO WHIRLING DISEASE, RESEARCHER SAYS
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 streams.
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 said.
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 niversity-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 Commerce.
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