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August 10, 2010

MADISON - The potentially deadly VHS fish virus did not spread to any inland Wisconsin waters that were tested for the virus in 2010, according to state fisheries officials. None of the fish that Department of Natural Resources fisheries biologist collected from nearly 70 lakes and rivers this spring tested positive for viral hemorrhagic septicemia.

"We're pleased that VHS hasn't spread inland and we appreciate the efforts that anglers and boaters have made to keep Wisconsin's fish healthy," says Mike Staggs, Wisconsin's fisheries director. "These results show that taking the prevention steps can contain the disease as well as help prevent the spread of other aquatic invasive species."

Earlier this year, Cornell University researchers reported finding VHS in Lake Superior fish collected in summer 2009, but no fish kills were evident in that lake in 2009 or 2010 because of VHS, and none of Wisconsin's 2010 testing suggested the virus had spread from that massive lake to inland lakes or streams.

"The good news is we assumed VHS was in Lake Superior when we developed the prevention rules in 2007, and as result, inland lakes and rivers were protected," Staggs says.

VHS can infect several dozen fish species in Wisconsin and can cause them to bleed to death; a recent Michigan State University study shows that muskellunge are most susceptible, followed by largemouth bass, yellow perch, rainbow trout, brook trout, brown trout, Chinook salmon, and coho salmon. The virus was first detected in Wisconsin in May 2007, when dead fish collected from the Lake Winnebago and Lake Michigan systems were tested and were positive for the virus. Lake Michigan fish again tested positive for the virus in 2008 and 2009. Information on VHS Distribution in Wisconsin is available on the DNR website.

2010 monitoring and hatchery system testing results

Wisconsin DNR tests fish for VHS for several different reasons: "surveillance" testing to learn where the virus is present and whether it's spread; to learn if the wild fish DNR uses to get eggs for state fish hatcheries have the virus; and before stocking fish back into lakes or rivers, according to Nick Legler, a fish health biologist who coordinated the VHS surveillance testing.

DNR also tests fish for VHS as part of investigating fish kills that occur in lakes or rivers, and to respond to anglers who report seeing fish with signs of VHS such as hemorrhages on the skin or internal organs, bulging eyes, and bloated abdomens.

DNR's 2010 surveillance testing was funded through a grant from the U.S. Department of Agriculture and involved DNR crews collecting 3,586 fish from 27 inland lakes and rivers throughout Wisconsin. The fish were all collected between March 24 and May 27, before the water temperatures rose above 60 degrees Fahrenheit, and the goal was to get a total of 150 fish from each water body of various species susceptible to the virus.

The fish were sent to one of three laboratories for testing: the U.S. Fish and Wildlife Service La Crosse Fish Health Center in Onalaska; the Wisconsin Veterinary Diagnostic Laboratory in Madison, and Micro Technologies in Richmond, Me.

Fish were tested from waters including Lake Monona in Dane County, Lac Courte Oreilles in Sawyer County, Shawano Lake in Shawano County, and Brule River Flowage in Florence County, and Rock Lake in Jefferson County.

The hatchery system testing was coordinated by Sue Marcquenski, DNR fish health specialist. The wild fish DNR collected eggs from for its hatchery operations were tested for VHS and other viruses. The resulting offspring of these fish were also tested for viruses about before they were transferred from DNR hatcheries into lakes or rivers. VHS was not detected in any fish from the state hatcheries.

Marcquenski said the wild broodfish are tested to find out whether they carry any virus that could be transmitted to other fish in the hatcheries. Their offspring are tested because at most DNR hatcheries, the fish are raised in outdoor facilities where they are exposed to birds, amphibians and mammals that can move fish pathogens from one place to another. "To be sure that the fish in the hatcheries are free of serious diseases, we test them for viruses about one month before they are stocked," she says.

Steps can help contain VHS and other aquatic invaders

Statewide surveys in fall 2008 and 2009, and surveys of boaters at boat landings in recent years suggest that the majority of boaters and anglers know about the three-year-old VHS rules and are following them. Those rules aim to prevent boaters and anglers from accidentally moving infected fish or water from one lake to another, Legler says. The VHS virus can survive in water for at least 14 days. Minnows can become infected with VHS after being exposed to VHS-contaminated water or fish, and game fish can become infected with VHS by eating infected minnows.

A few simple steps can help contain the disease and other aquatic invasive species such as Eurasian water-milfoil and zebra mussels.

FOR MORE INFORMATION CONTACT: Mike Staggs (608) 267-0796; Nick Legler (608) 264-6028; Sue Marcquenski (608) 266-2871

Last Revised: Tuesday, August 10, 2010

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