West Nile's Widening Toll - Washington Post 12/28/02

[Guest guest]

Saturday, 28 December 2002

 

WEST NILE'S WIDENING TOLL: Impact on North American Wildlife Far Worse Than on

Humans

 

by Rick Weiss

Washington Post Staff Writer

 

First there was the silence of the crows.

 

Then the horses fell ill -- more than 14,000 this past summer alone -- along

with

squirrels, chipmunks and mountain goats. Even mighty raptors -- eagles, hawks

and

great horned owls -- dropped from the sky.

 

Now scientists are beginning to take stock of West Nile virus's North American

invasion, and they are taken aback by the scale and sweep of its ecological

impact. While the human toll dominated the nation's attention this year -- the

virus killed at least 241 people and infected many thousands more -- the

effects on

wildlife were far worse.

 

The virus swept westward with alarming rapidity this year, appearing in almost

every state in the nation -- an astonishing expansion for a bug that had never

been

seen in the Western Hemisphere until three years ago. Equally unexpected,

nearly

200 species of birds, reptiles and mammals fell ill from West Nile this year,

including rabbits and reindeer, pelicans and bats, even a few dogs and cats.

The

virus also slammed dozens of exotic species in about 100 U.S. zoos, killing

cockatiels, emus, seals, flamingos and penguins. Florida alligator farms lost

more

than 200 of their reptiles.

 

"In my years of working, I've never seen a mosquito-borne virus spread so

quickly,"

said Robert G. McLean with the Agriculture Department's National Wildlife

Research

Center in Fort Collins, Colo.

 

Indeed, the epidemic has so resembled a bioterrorism attack that the nation's

zoos

-- which spearheaded an effort to track West Nile's march and to mount

emergency

vaccinations -- could end up with potentially important roles in the emerging

arena

of homeland security. Just last month, in a hastily organized effort

reminiscent

of President Bush's smallpox plan, officials at two California zoos inoculated

their endangered California condors with an experimental vaccine that may be

the

animals' only hope for survival.

 

West Nile is not fatal in all animals, and over time some species are expected

to

adapt. But even partial dropoffs in key populations could have serious

consequences. Rodent populations could blossom in areas where raptors are

dying,

and pest birds such as house sparrows may be increasing where crows are absent.

 

The worst is still ahead, scientists say. Come spring, West Nile is expected

to

complete its push to the West Coast, home to endangered whooping cranes and

economically important flocks of domestic geese. The virus is also poised to

leap

to the subtropics, where rare birds and other vulnerable creatures already face

formidable threats to their survival.

 

"Once it gets to the tropics, where you've got species already stressed by

habitat

destruction and you have the potential for year-round mosquito transmission,

some

of those populations are not going to make it," said Peter Marra, an animal

ecologist and West Nile specialist at the Smithsonian Environmental Research

Center

in Edgewater, Md. "I'm concerned about parrots and hummingbird populations.

There's not that many of them left."

 

NORTH AMERICAN DEBUT:

 

West Nile made its North American debut in the fall of 1999, discovered in a

dead

New York crow. Scientists don't know how the virus reached U.S. shores --

perhaps

it hid inside a single infected bird imported from the Middle East [:-)]. But

one

thing is certain, said Stephen Ostroff of the Centers for Disease Control and

Prevention (CDC) in Atlanta: "There's no way that West Nile is going to go

away."

 

The virus appears no more virulent in Americans than in other people around the

world, and scientists suspect that the population will gradually gain immunity

through low-level exposures. That is the situation today in countries where

the

virus has been active for many years. Most people in those countries have

antibodies to the virus from early childhood, and serious complications or

death

from West Nile are rare.

 

But in North American wildlife, the virus has proven to be unusually aggressive

and

capable of infecting a surprisingly diverse array of animals.

 

"Most viruses tend to be rather host-specific, but that's not the case with

what we

were seeing," said Tracey McNamara, chief of pathology for the Wildlife

Conservation Society, which has its headquarters at the Bronx Zoo, where the

first

infected crow was found.

 

It is still unclear how many of the 200 or so species struck by West Nile

infection

have suffered significant population declines. But a consensus is emerging

that

among birds, in particular, far more species are being hurt than scientists had

predicted -- not just the crows, ravens and jays that were known to be

especially

vulnerable.

 

"There's been a huge die-off of raptors," said McLean of the agriculture

department's Fort Collins lab.

 

The experience of the University of Minnesota's Raptor Center, which

rehabilitates

sick and injured raptors, was typical. "In mid-August, we had our first case:

a

great horned owl," said spokeswoman Sue Kirchoff. "In September and October,

we

were just inundated."

 

The center took in 70 ailing birds of prey, including great horned owls, eagles

and

red-tailed hawks. Officials there presume that if that many were found and

brought

to the center, countless others died in the wild, with potentially far-ranging

repercussions.

 

"From a biological standpoint, raptors take longer to mature and have fewer

offspring" than smaller birds, said Patti Bright of the American Bird

Conservancy.

"Whether they'll be able to rebound, well, we just don't know." It will take a

while longer, Bright and others said, before it is known whether rodent

populations

are taking advantage of West Nile's impact on birds of prey.

 

The evidence for declines in songbirds and other small avian species is less

direct, in part because they are so much less visible. "We're simply not going

to

know for a while with the smaller birds, because we're not going to find the

bodies," said David S. Wilcove, a professor of ecology at Princeton University

who

has been studying West Nile.

 

Still, researchers this year found more than 140 bird species sickened or dead

with

West Nile, including chickadees, doves, grackles, gulls, herons, kingfishers,

pelicans, sparrows, swans, turkeys, warblers, woodpeckers and wrens. And while

most of those species will probably pull through as resistant individuals mate

and

pass their antiviral vigor to their offspring, ornithologists expect that

others

will not be so lucky.

 

They point to the experience in Hawaii, where the arrival of avian pox virus in

the

1890s and avian malaria in the 1930s drove dozens of species to extinction or

close

to it. "Those viruses just hammered Hawaiian forest birds," Wilcove said.

"That

illustrates the potential for harm when a disease organism encounters a naïve

population."

 

BIRD-TO-BIRD INFECTION:

 

Several unexpected aspects of the epidemic have fed Wilcove's and others'

pessimism.

 

One surprise is that the virus can be transmitted directly from bird to bird,

not

only via mosquitoes. Raptors can acquire the virus by eating infected prey,

and

some birds can apparently spread the virus in their droppings. There's also

evidence that some birds can pass the virus directly to their chicks while

they're

still inside the egg.

 

Another surprise is that West Nile virus can be transmitted directly from adult

mosquitoes to their eggs, so that newly hatched aquatic larvae are born

infected.

***That could make insecticides, which typically kill only adults, less

effective.***

 

Scientists have also been surprised to learn that the virus can persevere

through

the winter, even in many Northern states. Researchers are not sure which

animals

are serving as the virus's winter host, but the phenomenon is allowing the

disease

to spread year round and is giving the summer viral eruption an earlier start

each

year.

 

Yet another surprise is the number of mosquito species -- 36 at last count --

that

carry the virus. "This is a virus that's Never Seen a Mosquito It Doesn't

Like,"

said Ostroff of the CDC. "That's not typical for most pathogenic viruses."

 

If that weren't enough, some researchers suspect that West Nile might be

capable of

mixing its genetic material with that of a closely related

virus, such as the one that causes St. Louis encephalitis, if both viruses were

to

infect a single animal. Other viruses have periodically produced such hybrids,

creating in the process an entirely new and dangerous bug.

 

"This virus is amazing," said CDC virologist Robert S. Lanciotti. "I've been in

this field almost 20 years, and I've never seen anything like it."

 

Neither has the state of California, but it is about to, experts say.

 

"It's going to spread to the West Coast big time by next year, no question,"

USDA's

McLean said. "Each habitat is different, but California seems to be an area

that

has all the factors you need for a major spread. I think they're going to be

facing major problems in humans, horses, birds and other animals. I just don't

see

any barriers."

 

Such predictions have a particularly ominous ring for researchers on the

California

Condor Recovery Team, who have been struggling to bring the ungainly bird back

from

the brink of extinction. They knew that this summer's experimental

inoculations of

zoo birds with the horse vaccine -- the only West Nile vaccine approved for

marketing in this country -- had been disappointing, with many birds failing to

develop protective antibodies. So in November, veterinarians at the Los

Angeles

and San Diego zoos injected into the thighs of their condors an experimental

vaccine to try to confer immunity before the spring egg-laying season.

 

"We had absolutely zero negative effects," said Cynthia Stringfield,

veterinarian

of the Los Angeles Zoo, and preliminary blood tests suggested that the birds

"had a

fantastic immune response."

 

If further tests show that the vaccine works, the team will try to vaccinate

all

128 captive California condors and the approximately 70 birds now living in the

wild.

 

WHAT ZOOS DO:

 

Zoos may take the lead in the fight against West Nile in more ways than that.

More

than 100 U.S. zoos and wildlife parks have joined a newly created

information-sharing network, which has its headquarters at Chicago's Lincoln

Park

Zoo, to track West Nile and other emerging infections in exotic animals.

 

Some scientists suspect the network may even prove useful in the cause of

homeland

security, by providing a sensitive, nationwide "sentinel system" for detecting

the

first hints of a bioterrorism attack. After all, zoo officials noted, New York

crows were dying in droves in the fall of 1999, but no one figured out that

West

Nile was the culprit -- or that the deaths were related to a spate of unusual

human

illnesses -- until a crow died on the grounds of the Bronx Zoo.

 

Zoos, it turns out, take every death seriously -- even those of non-zoo animals

on

zoo grounds -- because any death can mark the start of a devastating epidemic.

"Every dead animal is picked up and immediately necropsied," said McNamara, the

Bronx Zoo pathologist. "That's not true in Central Park."

 

When the Bronx crow was found to be teeming with West Nile, it was the first

evidence that the Old World virus had leaped the Atlantic -- and the beginning

of

the recognition that an epidemic was already underway in humans. With a system

in

place, McNamara said, a zoo vet could be the first to know if terrorists have

released a human or animal pathogen. The consortium is seeking federal funding.

 

Still, some scientists fear that the nation may soon become less able to

prevent

outbreaks such as that of West Nile -- whether accidental or intentional. They

said

the U.S. system for screening incoming animal, plant and microbial life -- a

patchwork of more than 20 agencies -- has long been undervalued and

underfunded.

Now the largest component, the Agriculture Department's Animal and Plant Health

Inspection Service, is to become part of the new Homeland Security Department.

That's leading many ecologists to fear that it will narrow its focus to

classical

bioterrorism pathogens such as anthrax, leaving the nation more vulnerable to

civilian bugs such as West Nile.

 

"I have a feeling that beetles in imported wood packaging are not going to be

at

the top of the list," said Faith T. Campbell, director of the invasive species

program at the American Lands Alliance in Washington. Yet the recent U.S.

invasion

by Asian longhorned beetles, which arrived in wood packaging from China, is

expected to cost the nation as much as $669 billion in insect-destroyed trees

in

urban areas alone in coming decades, Campbell said.

 

Whether West Nile ends up decimating many animal populations or settling in as

a

mere high-grade ecological disturbance, the epidemic should be a wake-up call

to

beef up the nation's surveillance and quarantine network, said Princeton's

Wilcove.

 

"We may be lucky this time and get by with minimal losses of human life and

minimal

losses of wildlife, but this is not going to be the last disease to get into

this

country," he said. "One of these days we're going to draw the short straw."

[Guest guest]

(re-formatted)

 

Saturday, 28 December 2002

 

WEST NILE'S WIDENING TOLL: Impact on North American Wildlife Far Worse Than on

Humans

 

by Rick Weiss

Washington Post Staff Writer

 

First there was the silence of the crows.

 

Then the horses fell ill -- more than 14,000 this past summer alone -- along

with

squirrels, chipmunks and mountain goats. Even mighty raptors -- eagles, hawks

and

great horned owls -- dropped from the sky.

 

Now scientists are beginning to take stock of West Nile virus's North American

invasion, and they are taken aback by the scale and sweep of its ecological

impact. While the human toll dominated the nation's attention this year -- the

virus killed at least 241 people and infected many thousands more -- the

effects on

wildlife were far worse.

 

The virus swept westward with alarming rapidity this year, appearing in almost

every state in the nation -- an astonishing expansion for a bug that had never

been

seen in the Western Hemisphere until three years ago. Equally unexpected,

nearly

200 species of birds, reptiles and mammals fell ill from West Nile this year,

including rabbits and reindeer, pelicans and bats, even a few dogs and cats.

The

virus also slammed dozens of exotic species in about 100 U.S. zoos, killing

cockatiels, emus, seals, flamingos and penguins. Florida alligator farms lost

more

than 200 of their reptiles.

 

"In my years of working, I've never seen a mosquito-borne virus spread so

quickly,"

said Robert G. McLean with the Agriculture Department's National Wildlife

Research

Center in Fort Collins, Colo.

 

Indeed, the epidemic has so resembled a bioterrorism attack that the nation's

zoos

-- which spearheaded an effort to track West Nile's march and to mount

emergency

vaccinations -- could end up with potentially important roles in the emerging

arena

of homeland security. Just last month, in a hastily organized effort

reminiscent

of President Bush's smallpox plan, officials at two California zoos inoculated

their endangered California condors with an experimental vaccine that may be

the

animals' only hope for survival.

 

West Nile is not fatal in all animals, and over time some species are expected

to

adapt. But even partial dropoffs in key populations could have serious

consequences. Rodent populations could blossom in areas where raptors are

dying,

and pest birds such as house sparrows may be increasing where crows are absent.

 

The worst is still ahead, scientists say. Come spring, West Nile is expected

to

complete its push to the West Coast, home to endangered whooping cranes and

economically important flocks of domestic geese. The virus is also poised to

leap

to the subtropics, where rare birds and other vulnerable creatures already face

formidable threats to their survival.

 

"Once it gets to the tropics, where you've got species already stressed by

habitat

destruction and you have the potential for year-round mosquito transmission,

some

of those populations are not going to make it," said Peter Marra, an animal

ecologist and West Nile specialist at the Smithsonian Environmental Research

Center

in Edgewater, Md. "I'm concerned about parrots and hummingbird populations.

There's not that many of them left."

 

NORTH AMERICAN DEBUT:

 

West Nile made its North American debut in the fall of 1999, discovered in a

dead

New York crow. Scientists don't know how the virus reached U.S. shores --

perhaps

it hid inside a single infected bird imported from the Middle East [:-)]. But

one

thing is certain, said Stephen Ostroff of the Centers for Disease Control and

Prevention (CDC) in Atlanta: "There's no way that West Nile is going to go

away."

 

The virus appears no more virulent in Americans than in other people around the

world, and scientists suspect that the population will gradually gain immunity

through low-level exposures. That is the situation today in countries where

the

virus has been active for many years. Most people in those countries have

antibodies to the virus from early childhood, and serious complications or

death

from West Nile are rare.

 

But in North American wildlife, the virus has proven to be unusually aggressive

and

capable of infecting a surprisingly diverse array of animals.

 

"Most viruses tend to be rather host-specific, but that's not the case with

what we

were seeing," said Tracey McNamara, chief of pathology for the Wildlife

Conservation Society, which has its headquarters at the Bronx Zoo, where the

first

infected crow was found.

 

It is still unclear how many of the 200 or so species struck by West Nile

infection

have suffered significant population declines. But a consensus is emerging

that

among birds, in particular, far more species are being hurt than scientists had

predicted -- not just the crows, ravens and jays that were known to be

especially

vulnerable.

 

"There's been a huge die-off of raptors," said McLean of the agriculture

department's Fort Collins lab.

 

The experience of the University of Minnesota's Raptor Center, which

rehabilitates

sick and injured raptors, was typical. "In mid-August, we had our first case:

a

great horned owl," said spokeswoman Sue Kirchoff. "In September and October,

we

were just inundated."

 

The center took in 70 ailing birds of prey, including great horned owls, eagles

and

red-tailed hawks. Officials there presume that if that many were found and

brought

to the center, countless others died in the wild, with potentially far-ranging

repercussions.

 

"From a biological standpoint, raptors take longer to mature and have fewer

offspring" than smaller birds, said Patti Bright of the American Bird

Conservancy.

"Whether they'll be able to rebound, well, we just don't know." It will take a

while longer, Bright and others said, before it is known whether rodent

populations

are taking advantage of West Nile's impact on birds of prey.

 

The evidence for declines in songbirds and other small avian species is less

direct, in part because they are so much less visible. "We're simply not going

to

know for a while with the smaller birds, because we're not going to find the

bodies," said David S. Wilcove, a professor of ecology at Princeton University

who

has been studying West Nile.

 

Still, researchers this year found more than 140 bird species sickened or dead

with

West Nile, including chickadees, doves, grackles, gulls, herons, kingfishers,

pelicans, sparrows, swans, turkeys, warblers, woodpeckers and wrens. And while

most of those species will probably pull through as resistant individuals mate

and

pass their antiviral vigor to their offspring, ornithologists expect that

others

will not be so lucky.

 

They point to the experience in Hawaii, where the arrival of avian pox virus in

the

1890s and avian malaria in the 1930s drove dozens of species to extinction or

close

to it. "Those viruses just hammered Hawaiian forest birds," Wilcove said.

"That

illustrates the potential for harm when a disease organism encounters a naïve

population."

 

BIRD-TO-BIRD INFECTION:

 

Several unexpected aspects of the epidemic have fed Wilcove's and others'

pessimism.

 

One surprise is that the virus can be transmitted directly from bird to bird,

not

only via mosquitoes. Raptors can acquire the virus by eating infected prey,

and

some birds can apparently spread the virus in their droppings. There's also

evidence that some birds can pass the virus directly to their chicks while

they're

still inside the egg.

 

Another surprise is that West Nile virus can be transmitted directly from adult

mosquitoes to their eggs, so that newly hatched aquatic larvae are born

infected.

***That could make insecticides, which typically kill only adults, less

effective.***

 

Scientists have also been surprised to learn that the virus can persevere

through

the winter, even in many Northern states. Researchers are not sure which

animals

are serving as the virus's winter host, but the phenomenon is allowing the

disease

to spread year round and is giving the summer viral eruption an earlier start

each

year.

 

Yet another surprise is the number of mosquito species -- 36 at last count --

that

carry the virus. "This is a virus that's Never Seen a Mosquito It Doesn't

Like,"

said Ostroff of the CDC. "That's not typical for most pathogenic viruses."

 

If that weren't enough, some researchers suspect that West Nile might be

capable of

mixing its genetic material with that of a closely related

virus, such as the one that causes St. Louis encephalitis, if both viruses were

to

infect a single animal. Other viruses have periodically produced such hybrids,

creating in the process an entirely new and dangerous bug.

 

"This virus is amazing," said CDC virologist Robert S. Lanciotti. "I've been in

this field almost 20 years, and I've never seen anything like it."

 

Neither has the state of California, but it is about to, experts say.

 

"It's going to spread to the West Coast big time by next year, no question,"

USDA's

McLean said. "Each habitat is different, but California seems to be an area

that

has all the factors you need for a major spread. I think they're going to be

facing major problems in humans, horses, birds and other animals. I just don't

see

any barriers."

 

Such predictions have a particularly ominous ring for researchers on the

California

Condor Recovery Team, who have been struggling to bring the ungainly bird back

from

the brink of extinction. They knew that this summer's experimental

inoculations of

zoo birds with the horse vaccine -- the only West Nile vaccine approved for

marketing in this country -- had been disappointing, with many birds failing to

develop protective antibodies. So in November, veterinarians at the Los

Angeles

and San Diego zoos injected into the thighs of their condors an experimental

vaccine to try to confer immunity before the spring egg-laying season.

 

"We had absolutely zero negative effects," said Cynthia Stringfield,

veterinarian

of the Los Angeles Zoo, and preliminary blood tests suggested that the birds

"had a

fantastic immune response."

 

If further tests show that the vaccine works, the team will try to vaccinate

all

128 captive California condors and the approximately 70 birds now living in the

wild.

 

WHAT ZOOS DO:

 

Zoos may take the lead in the fight against West Nile in more ways than that.

More

than 100 U.S. zoos and wildlife parks have joined a newly created

information-sharing network, which has its headquarters at Chicago's Lincoln

Park

Zoo, to track West Nile and other emerging infections in exotic animals.

 

Some scientists suspect the network may even prove useful in the cause of

homeland

security, by providing a sensitive, nationwide "sentinel system" for detecting

the

first hints of a bioterrorism attack. After all, zoo officials noted, New York

crows were dying in droves in the fall of 1999, but no one figured out that

West

Nile was the culprit -- or that the deaths were related to a spate of unusual

human

illnesses -- until a crow died on the grounds of the Bronx Zoo.

 

Zoos, it turns out, take every death seriously -- even those of non-zoo animals

on

zoo grounds -- because any death can mark the start of a devastating epidemic.

"Every dead animal is picked up and immediately necropsied," said McNamara, the

Bronx Zoo pathologist. "That's not true in Central Park."

 

When the Bronx crow was found to be teeming with West Nile, it was the first

evidence that the Old World virus had leaped the Atlantic -- and the beginning

of

the recognition that an epidemic was already underway in humans. With a system

in

place, McNamara said, a zoo vet could be the first to know if terrorists have

released a human or animal pathogen. The consortium is seeking federal funding.

 

Still, some scientists fear that the nation may soon become less able to

prevent

outbreaks such as that of West Nile -- whether accidental or intentional. They

said

the U.S. system for screening incoming animal, plant and microbial life -- a

patchwork of more than 20 agencies -- has long been undervalued and

underfunded.

Now the largest component, the Agriculture Department's Animal and Plant Health

Inspection Service, is to become part of the new Homeland Security Department.

That's leading many ecologists to fear that it will narrow its focus to

classical

bioterrorism pathogens such as anthrax, leaving the nation more vulnerable to

civilian bugs such as West Nile.

 

"I have a feeling that beetles in imported wood packaging are not going to be

at

the top of the list," said Faith T. Campbell, director of the invasive species

program at the American Lands Alliance in Washington. Yet the recent U.S.

invasion

by Asian longhorned beetles, which arrived in wood packaging from China, is

expected to cost the nation as much as $669 billion in insect-destroyed trees

in

urban areas alone in coming decades, Campbell said.

 

Whether West Nile ends up decimating many animal populations or settling in as

a

mere high-grade ecological disturbance, the epidemic should be a wake-up call

to

beef up the nation's surveillance and quarantine network, said Princeton's

Wilcove.

 

"We may be lucky this time and get by with minimal losses of human life and

minimal

losses of wildlife, but this is not going to be the last disease to get into

this

country," he said. "One of these days we're going to draw the short straw."