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Fish-killing virus now found in all Great Lakes in US

The virus, which has been identified in 28 freshwater fish species in the Great Lakes watershed, has reached epidemic proportions in the Great Lakes and threatens New York's sport-fishing industry.

Fish-killing virus now found in all Great Lakes in US

Reports indicate that a deadly fish virus that was first discovered in the Northeast in 2005, has been found for the first time in fish from Lake Superior, which means that the virus has now been documented in all of the Great Lakes in the US.

The viral hemorrhagic septicemia virus (VHSV), which causes fatal anemia and hemorrhaging in many fish species, poses no threat to humans, Paul Bowser, professor of aquatic animal medicine at Cornell's College of Veterinary Medicine, told Chronicle Online.

Bowser and colleagues recently tested 874 fish from seven sites in Lake Superior in collaboration with the US Geological Survey (USGS) Western Fisheries Research Center in Seattle.

Fish from Paradise and Skanee in Michigan and St Louis Bay and Superior Bay in Wisconsin tested positive.

The virus, which has been identified in 28 freshwater fish species in the Great Lakes watershed, has reached epidemic proportions in the Great Lakes and threatens New York's sport-fishing industry, estimated to contribute some $1.4 billion annually to New York's economy.

"People come from all over the eastern United States to fish the Great Lakes," said Bowser, noting that the virus has also been found in a few inland waters as well, including lakes, streams and a family-owned earthen pond.

"On a worldwide basis, VHSV is considered one of the most serious pathogens of fish, because it kills so many fish, is not treatable and infects a broad range of fish species," he said.

In 2008, the US Department of Agriculture issued a federal order preventing transport of the 28 species within the Great Lakes watershed, including Lake Superior, to limit the spread of this viral pathogen.

As a result, the new findings will not lead to additional regulatory actions, according to authorities.

While no significant fish mortality due to VHSV was observed in 2008 and 2009, "It is important to note that there are still fish harboring VHSV; essentially the infection proceeds even though no mortalities are being observed," said Bowser.

"This is important because it suggests that these infected fish may serve as a reservoir for the virus in the Great Lakes ecosystem. While we don't fully understand the lack of recent mortality, the potential presence or absence of stressors on the fish may be playing a role," he added.

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