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A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Thu 6 May 2010
Source: PhysOrg.com [edited]
Study suggests fish virus spread by fish, not boats
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Viral hemorrhagic septicemia virus could be in a lake without killing
fish, according to a new study on the deadly virus that threatens New
York's billion dollar sport-fishing industry. Ships may not have
recently introduced a deadly virus that has killed large numbers of
fish in several Great Lakes since 2005 as previously thought, reports
a new Cornell study [see below for the reference & link], but the
virus may have been present for decades.
Its new finding is that "viral hemorrhagic septicemia virus (VHSV)
could be in a lake without killing fish," said Mark Bain, associate
professor of natural resources and lead author of a paper published
online in the journal Public Library of Science One (Vol. 5: 4).
"Healthy fish can carry this disease at low levels," said Bain. "That
means the eruption of fish kills from VHSV does not signal its arrival."
After large numbers of fish inexplicably died in Lake Ontario in
2005, researchers at Cornell's College of Veterinary Medicine
identified the culprit as VHSV, which causes anemia and hemorrhaging
in fish but is harmless to humans. It was the 1st time the virus had
been documented in a Great Lake. The researchers had assumed that
ships had recently introduced the virus.
The new study, however, reports that VHSV is prevalent in the waters
and fish everywhere they tested in Lakes Huron, Erie, and Ontario,
leading them to think the virus may have been living in fish
undetected in the lakes for decades, casting doubt on the theory that
ships introduced the virus.
Until now, researchers had only tested samples from dead fish. The
new study involved analyzing samples, for the 1st time, from live
fish and water from 30 locations across the 3 Great Lakes, including
10 harbors, 10 boating centers, and 10 wild shorelines. "We found it
everywhere, not just around fishing harbors and boating centers,"
said Bain. "We have no evidence that this pathogen is concentrated
around shipping." The researchers do not know how the virus initially
entered the Great Lakes, but VHSV has existed historically in the
North Atlantic and in Europe.
Since 2005, large VHSV-related fish kills have occurred in Lakes
Ontario, Huron, and Erie, in the St Lawrence and Niagara Rivers, and
VHSV has been identified in Lake Superior and smaller lakes,
including the western-most Finger Lake in New York, Conesus Lake.
Researchers have detected the virus in more than 20 Great Lakes fish
species, posing a potential threat to New York's USD 1.2 billion
sport-fishing industry. Authorities have responded with strict
regulations on boats and ballast water and on moving fish and bait
minnows between lakes.
One theory why VHSV started killing fish in large numbers in 2005 is
that warmer springs led to rapid rises in water temperatures, which
stresses fish during spawning periods and makes them more susceptible
to the virus, said Bain. Another theory: that over the last 10 years,
round goby -- known carriers of the virus -- has been spreading in
the Great Lakes and may be shedding VHSV in the water.
"It's the most infected fish," said Bain. "It may be that higher
populations of round goby brought the disease to more prominence."
[Byline: Krishna Ramanujan]
--
Communicated by:
ProMED-mail
[The paper itself is available on PLoS ONE:
Bain MB, Cornwell ER, Hope KM, Eckerlin GE, Casey RN, et al:
Distribution of an Invasive Aquatic Pathogen (Viral Hemorrhagic
Septicemia Virus) in the Great Lakes and Its Relationship to
Shipping. 2010. PLoS ONE 5(4): e10156. doi:10.1371/journal.pone.0010156
The report above in PhysOrg is more informative than the paper's
abstract. - Mod.MHJ]
[The Great Lakes can be seen on the HealthMap/ProMED-mail interactive
map of the USA at
[see also:
Viral hemorrhagic septicemia, fish - USA (02): Lake Superior 20100415.1219
Viral hemorrhagic septicemia, fish - USA: (Lake Superior) 20100130.0325
Viral hemorrhagic septicemia, fish - USA: (MI) 20090903.3103
Viral hemorrhagic septicemia, fish - USA (02): (OH) 20080708.2072
Viral hemorrhagic septicemia, fish - USA: (OH) 20080611.1842
Viral hemorrhagic septicemia, fish - USA (NY) 20070622.2012
Viral hemorrhagic septicemia - USA (Lake Michigan) 20070526.1679
Viral hemorrhagic septicemia, fish - USA (MI,WI) 20070519.1595
Viral hemorrhagic septicemia, fish - USA (Lake Erie) 20070501.1418
Viral hemorrhagic septicemia, fish - USA (MI) 20070127.0353
Viral hemorrhagic septicemia, fish - USA (multistate): ban 20061029.3102]
...................................mhj/mj/dk
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