July 20, 2006 —
Cornell researchers have found that a deadly fish virus detected in the
northeastern United States for the first time in June in two species
has probably spread to at least two more. But they have yet to
determine whether the virus is responsible for the death of hundreds of
fish in Lake Ontario and the St. Lawrence River in recent weeks.
Over
the past month, Cornell’s Aquatic Animal Health Program at the College
of Veterinary Medicine has been sent some 300 fish for evaluation. The
frozen samples are from the fish that have been dying since late May
and early June in Lake Erie, Lake Ontario and the St. Lawrence River.
Last week, an estimated 1,000 dead fish washed up on the shores of Lake
Ontario in just one morning.
Viral hemorrhagic septicemia virus (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 causes fatal anemia and hemorrhaging in many fish species but poses no threat to humans or other animals.
"The
situation right now is that we still have fish dying in Lake Ontario,"
said Geoffrey Groocock, a postdoctoral associate at Cornell’s Aquatic
Animal Health Program.
"We have detected the virus in other fish
species in the region, which may be contributing to the continuing fish
mortalities. We are continuing to test samples as we receive them from
the New York State Department of Environmental Conservation (DEC) and
State University of New York College of Environmental Science and
Forestry Thousand Island Biological Field Station to try and get a
clearer picture."
The researchers are using a classical cell
culture technique to perform the initial stage of the diagnostic
testing. This technique can take two to four weeks to yield results.
Cornell researchers are developing a molecular-based test for VHSV
based on a specific gene sequence in the virus. Once available, the new
technique will cut the turnaround for confirmation to three to five
days.
Groocock said the high number of dead fish reported
recently may be due to the increased presence of vacationers on the
lakes in summer, as well as the increased awareness since reports of
mortalities earlier in the season. Also, recent storms and heavy winds
may have washed up more fish from deeper waters. Groocock added that
while more species of fish are dying, absolute numbers of fish
mortalities do not appear to be changing.
"There is no cure for
VHSV in fish in an ecosystem as large as the Great Lakes Basin. Given
this, it is likely that management practices designed to limit the
spread of the virus will be put in place," said Groocock.
Although
no management decisions have yet been made, the DEC could recommend
that boaters clean their boats before traveling from one body of water
to another and not dump bait minnows into open water after a day of
fishing.
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.
Source : Cornell University
