Should have cut and copied the first time. So sorry....
WEST NILE VIRUS, RAPTORS - USA (02)
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A ProMED-mail post
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International Society for Infectious Diseases
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Date: Wed 25 Sep 2002
From: ProMED-mail <promed@xxxxxxxxxxxxxx>
Source: Philadelphia Inquirer, Wed 25 Sep 2002 [edited]
<http://www.philly.com/mld/inquirer/4144030.htm>
Influx of Sick Raptors
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Across the region, wildlife rehabilitators are seeing an influx of raptors,
especially great horned owls and red-tailed hawks, with apparent
neurological problems. Veterinarians treating the birds think they know
what the problem is: West Nile virus is hitting the raptor population.
"There's a very definite, substantial die-off of birds of prey in
Pennsylvania," said Daniel Brauning, an ornithologist with the Pennsylvania
Game Commission. "There's a serious problem afoot here," echoed Jeanne
Woodford, president of the Woodford Cedar Run Wildlife Refuge in Medford,
Burlington County, which in the last month has treated at least 10 raptors
suspected of being infected with West Nile virus. This month alone,
Tri-State Bird Rescue in Newark, Delaware, has treated 9 great horned owls
and 3 red-tailed hawks. The rescue workers say they are confident about
their West Nile virus diagnosis, but cannot be sure of it because their
non-profit centers cannot afford to conduct definitive tests, and publicly
funded labs are backed up.
What concerns wildlife officials most, perhaps, is that while crows and
blue jays, the birds most commonly affected, are numerous enough to
withstand population losses, many raptor species are not. Pennsylvania
officials are especially worried about the potential impact on eagles,
peregrine falcons, ospreys and short-eared owls, all of which are either
endangered or threatened in the state. "In those lower populations, 10
birds is significant," said Jerry Feaser, a game commission spokesman.
Nationwide, all but the falcons have been identified as species that have
tested positive for West Nile virus. Largely due to an aggressive
restoration program, Pennsylvania now has 62 pairs of bald eagles, which
produced 87 young this year. If West Nile virus was to hit the birds,
Brauning said, "it could set the restoration program back 15 years."
Researchers are not sure why they are seeing an effect on raptors. They
theorize it could simply be a matter of these large birds being more
visible, so when they get sick people notice. Or, said Wendy Looker,
director of Rehabitat, a York County raptor rehab center, it could relate
to raptors being at the top of the food chain. A sick raptor might be
around longer to be noticed as compared to, say, a tiny songbird that would
be picked off by a predator at the first sign of weakness. Looker has seen
pockets of sick raptors. In York County, the numbers are low, she said. In
Dauphin County, right across Susquehanna River, "we have received as many
as 8 birds in 36 hours." Still, the situation in Pennsylvania and New
Jersey is nothing like that in the Midwest, particularly Ohio, where West
Nile virus has killed up to 1000 raptors since mid-August.
Now, with the fall migration just beginning, officials are alerting
researchers along the Mississippi flyway and into Mexico and Central
America so that they can develop better surveillance programs. "We are
expecting the virus will show up down there," said Emi Saito, a veterinary
medical officer with the National Wildlife Health Center in Madison, Wis.
The virus was first detected in New York City in 1999, and "this is the
first season we've experienced such a high morbidity among raptors," Saito
said. "Is it that West Nile virus has established itself so well that the
birds are being exposed? Or is something else going on that weakens the
birds? Has the virus changed in some way?" The virus "could be more
prevalent or more virulent or possibly both," said Len Soucy of the Raptor
Trust in Morrisville, N.J.
The national wildlife lab has begun testing dead birds for a host of
potential problems. "We want to find out, even if they test positive for
West Nile virus, whether that's what's killing them," Saito said. The spike
in sickened raptors may say something about how the virus is spreading. So
far, all researchers know is that it spreads by bites from mosquitoes
infected with West Nile. But they are wondering now whether it can also be
transmitted to birds who ingest mice or other small animals with the virus.
Researchers also are looking at a species of blood-sucking fly, found in
small numbers on all wild birds. [This may be a reference to ectoparasitic
flies of the family _Hippoboscidae_. - Mod.CP] Looker said rehabbers are
finding hundreds of them on sick birds. A state lab has confirmed that
flies she collected were infected. But what does that mean? "Are the flies
a host? Can they transmit?" Looker said. "There are more questions than
answers." Some facilities, including the Raptor Trust and Rehabitat, have
begun to experiment with the only West Nile vaccine in existence -- one for
horses -- administering it in low doses to resident raptors used for
educational purposes. "We're pretty much shooting in the dark," Soucy said.
They think the vaccine is innocuous. Then again, they're not sure whether
it's protecting the birds. What they would like to see is for some infected
wild birds to recover, which would suggest they had built up antibodies
that could be passed along to others in the population. But so far, the
birds are either dying or do not recover enough to be released, said Sallie
Welte, a veterinarian at Tri-State. This, despite "intensive supportive
care" that includes Vitamin B injections, anti-fungal medication,
antibiotics, echinacea as an immune stimulant and a diet heavy on liquids
and easy-to-digest foods."When its gets into an area where there are no
natural immunities, that's when it hammers the wildlife," Soucy said.
Actually, he is almost more worried about the public reaction than about
West Nile virus. "I don't want to... regress 40 years and start spraying
the whole world with DDT." "I think the point is that we are going to have
to learn to live with this disease, as we have had to learn to deal with
the AIDS virus and the common cold," he said. Feaser agrees. "Bottom line,
although we will be monitoring the impacts, if any, of West Nile virus on
the bird and mammal populations, there is basically nothing that can be
done to intervene in the process... . Wildlife populations will have to
adapt to the disease."
[By Sandy Bauers]
--
ProMED-mail
<promed@xxxxxxxxxxxxxx>
[This article highlights some of the unresolved problems in this alarming
situation: namely, the high morbidity observed in 2002 in contrast to
previous years; the uncertain identity of the potential vector - mosquito
or ectoparasite; an apparent regional variation in morbidity and mortality;
the protective efficacy or not of immunization employing an equine vaccine;
and the unavoidable reliance on circumstantial evidence in the diagnosis of
West Nile virus infection. - Mod.CP]
[see also:
West Nile virus, raptors - USA 20020912.5289
West Nile virus, hippoboscid flies - USA (PA) 20020925.5395 ]
..........................dk/mpp/cp/mpp
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