Reasonable Rascal
09-25-02, 23:03
WEST NILE VIRUS, RAPTORS - USA (02)
***********************************
A ProMED-mail post
Date: Wed 25 Sep 2002
Source: Philadelphia Inquirer, Wed 25 Sep 2002 [edited]
<http://www.philly.com/mld/inquirer/4144030.htm>
Influx of Sick Raptors
----------------------
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
[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]
--------------------------------------------------
Several points in this article that stand out in my mind:
1. WNV can very conceivably have a detrimental effect on wildlife backgrounds. While songbirds traditionally have large populations raptors do not. There is also a species of crane in the US potentially being threatened with extinction due to the effects of WNV, largely in part due to the gact that the total remaining numbers are limited to a couple hundred birds.
2. The possibility that not only mosquitos but now certain flies may also be transmittal vectors for WNV.
[This may be a reference to ectoparasitic flies of the family _Hippoboscidae_. - Mod.CP]
3. The question raised as to whether the virus is merely more prevalent now [in raptors] or whether it may have mutated into a more virulent form. This same question might easily be applied to the significant increase in human cases across the US this season, and the cocommittant infection across species to now include dogs, squirrels and pack animals other than horses (llamas and alpacas).
The progression of this emergent disease in North America has proven to be very instructive, however it was introduced here 3 years ago.
RR
***********************************
A ProMED-mail post
Date: Wed 25 Sep 2002
Source: Philadelphia Inquirer, Wed 25 Sep 2002 [edited]
<http://www.philly.com/mld/inquirer/4144030.htm>
Influx of Sick Raptors
----------------------
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
[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]
--------------------------------------------------
Several points in this article that stand out in my mind:
1. WNV can very conceivably have a detrimental effect on wildlife backgrounds. While songbirds traditionally have large populations raptors do not. There is also a species of crane in the US potentially being threatened with extinction due to the effects of WNV, largely in part due to the gact that the total remaining numbers are limited to a couple hundred birds.
2. The possibility that not only mosquitos but now certain flies may also be transmittal vectors for WNV.
[This may be a reference to ectoparasitic flies of the family _Hippoboscidae_. - Mod.CP]
3. The question raised as to whether the virus is merely more prevalent now [in raptors] or whether it may have mutated into a more virulent form. This same question might easily be applied to the significant increase in human cases across the US this season, and the cocommittant infection across species to now include dogs, squirrels and pack animals other than horses (llamas and alpacas).
The progression of this emergent disease in North America has proven to be very instructive, however it was introduced here 3 years ago.
RR