Deadly VHS Virus Found in Lake Huron

[Lee Borgersen]

DNR: Deadly VHS Virus Found in Lake Huron

January 27, 2007

BY ERIC SHARP

FREE PRESS OUTDOORS WRITER

Viral hemorrhagic septicemia has been confirmed in Lake Huron whitefish, walleyes and Chinook salmon, the Department of Natural Resources said Friday, raising concerns the disease soon will reach lakes Michigan and Superior.

Previously known only in saltwater fish in North America, VHS was first recognized in Lake Ontario two years ago. Last summer it spread to lakes Erie and St. Clair. The strain of VHS was very similar to one found in the Canadian Maritime provinces, and many biologists believe it reached the Great Lakes in the ballast water of oceangoing ships.

The virus caused large kills of muskellunge, bluegills, perch, sheepshead and other species in the two lower Great Lakes. Walleyes were not affected in Erie or Ontario, but were carriers, and biologists believe VHS caused a kill of walleyes and whitefish near Thunder Bay in Lake Huron last fall.

The VHS kill at Thunder Bay could not be confirmed because the fish were badly decomposed and botulism bacteria also were found in the area. But biologists said VHS was the likely cause, and because VHS was confirmed in whitefish in the Cheboygan area and in Chinook salmon at the Swan River egg-collecting station near Rogers City.

VHS causes the gills and internal organs of fish to swell and bleed, but it does not affect people. It seems to be most lethal in young fish during spring and fall spawning periods when water temperatures are 38-58 degrees.

The U.S. Department of Agriculture and the Province of Ontario have imposed restrictions on the movement of live fish in the Great Lakes area in an effort to contain the spread of the disease.

Kelley Smith, who heads the DNR's fisheries division, said, "We went back and reanalyzed some tissue samples and found the disease was in Lake St. Clair as early as 2003.

"We can't stop it and we can't eradicate it, so we are concentrating on how we can slow the spread and buy ourselves some time."

Smith said while researchers would try to develop a VHS vaccine, the best hope might be that Great Lakes fish develop immunity through exposure.