FISH VIRUS SPREADING TO NEW SPECIES
January 2009 UPDATE - The Wisconsin Department of Natural Resources reported Thursday that two sport fish have tested positive for a fatal viral disease, and for the first time, the disease has been found in Lake Michigan. The DNR said that a smallmouth bass tested positive for viral hemorrhagic septicemia in Sturgeon Bay and a brown trout also tested positive in Lake Michigan near Algoma in Kewaunee County.
Known as viral hemorrhagic septicemia, VHS, the virus has been detected in eight Great Lakes states and two Canadian provinces, and affects 39 different species of fish. Several of the species affected are favorites of freshwater fishing and are important in the aquaculture industry, including largemouth and smallmouth bass, crappie, bluegill and perch. The virus poses no threat to humans or seafood, but it is easily spread among fish and could have a devastating impact on fish populations.
There is no known cure for the virus, which causes bleeding of the fish's tissues, including internal organs. A federal order issued by the U.S. Department of Agriculture's Animal and Plant Health Inspection Service in November 2006 prohibits the movement of affected species from state to state unless the fish are tested for and documented as being free of the virus.
In late spring of 2006, thousands of dead fish began washing up on the shores of Lake Ontario. Although testing is continuing at Cornell University's Aquatic Animal Health Program at the College of Veterinary Medicine, it appears that a new fish virus, Viral hemorrhagic septicemia virus (VHSV, is responsible. The virus destroys tissue in the vital organs, causing lethal internal bleeding in fish, but is not communicable to humans. The disease was first detected in the Pacific Northwest, but scientists believe the virus mutated into a strain more contagious than the one in the Pacific Northwest.
Cornell researchers have found that the virus, which was detected in the northeastern United States for the first time in June in two species has probably spread to at least two more. VHSV was detected and confirmed for the first time in the Northeast in round gobies and muskellunge in June. Cornell researchers are awaiting finals results of tests on 54 fish of 10 species that indicated VHSV in smallmouth bass and burbot. To date, Cornell researchers also have tested for the virus in lake sturgeon, brown bullhead, rock bass, yellow perch, pumpkinseed and black crappie.
VHSV was first reported in 1988 in the United States in spawning salmon in the Pacific Northwest. It was reported in North American freshwater fish in 2005 in muskellunge in Lake St. Claire, Mich., and in freshwater drum from the Bay of Quinte, Lake Ontario, Canada.
