MSNBC Bird flu not taking wing on migratory pathways

[Guest guest]

>http://www.msnbc.msn.com/id/10624217/

>

 

Bird flu not taking wing on migratory pathways

Disease appears more likely to make its away around the globe by airplane

The Associated Press

Updated: 9:43 a.m. ET Dec. 28, 2005

 

 

WASHINGTON - Bird flu appears more likely to wing

its away around the globe by plane than by

migrating birds.

 

Scientists have been unable to link the spread of

the virus to migratory patterns, suggesting that

the thousands of wild birds that have died,

primarily waterfowl and shore birds, are not

primary transmitters of bird flu.

 

If that holds true, it would suggest that

shipments of domestic chickens, ducks and other

poultry represents a far greater threat than does

the movement of wild birds on the wing.

 

It also would underscore the need to pursue the

virus in poultry farms and markets rather than in

wild populations of birds if a possible pandemic

is to be checked, U.S. and European experts said.

 

The H5N1 strain has infected millions of poultry

throughout Asia and parts of Europe since 2003.

The virus also has killed at least 71 people,

many of whom had close contact with poultry.

 

To date, the virus hasn't been shown to spread

from person to person, but many fear that it

could mutate into a strain that could,

potentially killing millions in a global pandemic.

 

While the prospect that migrating birds could

carry the virus worldwide still worries health

authorities, that sort of scenario doesn't appear

to be playing out.

 

" There is more and more evidence building up that

wild migratory birds do play some role in

spreading the virus, but personally I believe -

and others agree - that it's not a major role, "

said Ward Hagemeijer, a wild bird ecologist with

Wetlands International, a conservation group in

Wageningen, Netherlands. " If we would assume

based on this evidence that wild birds would be a

major carrier of the disease we would expect a

more dramatic outbreak of the disease all over

the world. "

 

Reports this summer and fall of the spread of the

H5N1 strain strongly suggested wild birds were

carrying the disease outward from Asia as they

followed migration patterns that crisscross the

Earth. The timing and location of outbreaks in

western China, Russia, Romania, Turkey and

Croatia seemed to point to wild birds en route to

winter grounds.

 

That put places like Alaska, where birds from the

Old and New Worlds gather each summer to create

what some call an " international viral transfer

center, " on alert that the virus could arrive

this coming spring. And from there, species like

the buff-breasted sandpiper and others that split

their time between North and South America could

in theory transport the virus farther afield.

 

Since the early fall, however, there have been

only scattered reports of more outbreaks. The

disease has been glaringly absent, for example,

from western Europe and the Nile delta, where

many presumed it would crop up as migrating birds

returned to winter roosts.

 

That suggests the strain has evolved to

specifically exploit domestic poultry, whose

short lives spent in tight flocks mean a virus

has to skip quickly from bird to bird if it is to

survive, said Hon Ip, a virologist with the U.S.

Geological Survey's National Wildlife Health

Center in Madison, Wis.

 

That also means that while the virus can pass

from domestic to wild birds, the latter may not

be suited as transmitters of the strain - at

least so far.

 

" By the timing of the spread and the pattern of

outbreaks within a country and between countries,

it does not make sense relative to a role for

migratory birds as a means of spreading the

virus, " Ip said.

 

For example, the virus killed thousands of

bar-headed geese in May and June at Lake Qinghai

in western China. The deaths raised immediate

fears that the virus was on the move, jumping

among hosts in the wild. In the Aug. 19 issue of

the journal Science, scientists wrote that the

virus " has the potential to be a global threat. "

 

But Ip and others suggest the lake is not as

remote and pristine as initially portrayed, and

that poultry raised in the area could have been

the source of the flu strain that killed the

geese.

 

" It is still patchy - the pattern of outbreaks -

to really make a very definitive link between

migratory birds and the disease, " said Marco

Barbieri, the scientific and technical officer

for the United Nations Environmental Program's

convention on migratory species in Bonn, Germany.

 

Experts caution that wild birds cannot be ruled

out as future transmitters of the H5N1 strain,

which has yet to be detected in North America.

Migratory birds, for example, have been clearly

implicated in the spread of West Nile virus,

which has killed at least 762 people in the U.S.

since 2002.

 

The H5N1 flu strain already is known to be lethal

to nearly 60 species of birds; further mutations

of the strain could allow it to infect many more.

One of the latest victims is the Asian tree

sparrow, according to a study published in the

December issue of the Journal of Virology.

 

" The dogma right now is it is the waterfowl -

ducks, sandpipers, gulls, plovers - essentially

any bird that is water-associated, " said A.

Townsend Peterson, a University of Kansas

professor and curator of the school's Natural

History Museum and Biodiversity Research Center.

" I will predict that that dogma will eventually

fall by the wayside. I will guess that what we

will eventually see is that avian influenza is

much more widely distributed among birds and that

land birds also play a significant role in the

picture. "

 

That has made increasing the understanding of the

migratory routes followed by birds more important

than ever. It also draws attention to how little

is still known about the routes.

 

The conventional maps that show flyways as fat

arrows that can span continents and oceans lack

the nuance and detail of how birds really move,

including when and in what numbers, experts said.

The maps also can gloss over how migratory

patterns can vary among subspecies.

 

Traditional methods like bird watching and

banding are helping flesh out the maps. And now

tracking by satellite or radio, as well as

genetic and isotopic sampling, are playing an

increased role in sussing out the finer details

of where birds travel and when.

 

In places like Alaska, where millions of

individual birds representing more than 200

species arrive each spring, scientists readily

confess the situation isn't all clear.

 

" Fuzzy would be an operative word. We are in the

process of defining the Alaskan migration system,

and it is remarkably complex, " said Kevin Winker,

curator of birds and an associate professor at

the University of Alaska, Fairbanks.

 

In the United States, the U.S. Geological Survey,

Fish and Wildlife Service and the Agriculture

Department plan next year to step up their

surveillance of wild flocks of birds.

 

In the past several weeks, scientists have

winnowed down their list of birds they want to

keep tabs on, said Dirk Derksen, a biologist with

the USGS Alaska Science Center in Anchorage. All

spend at least part of the year in Asia.

 

Early detection would buy time in forestalling

the further spread of the virus - a situation no

one wants.

 

" Initially, wild birds are primarily victims.

Someday they may become vectors. We don't know

how that will play out, " Ip said. " What I would

like to see is the virus stopped before it gets

to America so we don't see the last reel of this

film played out in North America. "

© 2005 The Associated Press. All rights reserved.

This material may not be published, broadcast,

rewritten or redistributed.

 

© 2005 MSNBC.com

 

URL: http://www.msnbc.msn.com/id/10624217/

--