(MY) don't blame wild birds

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Tuesday March 28, 2006- The Star

 

Don't blame wild birds

 

By TAN CHENG LI

 

It is possible – wild birds are capable of carrying the highly

pathogenic H5NI virus. After all, there are at least 144 strains of

avian influenza circulating in wild birds. Most, however, are at low

levels and at worst, cause only mild disease.

 

But with the deadly H5N1, the scales are tilted towards wild birds

being victims rather than vectors of the virus.

 

The argument of bird experts, who insist that migratory birds have

been made a scapegoat in the spread of the virus, rests on these

points: the pattern of avian influenza outbreaks does not coincide

with bird migratory routes or timelines; the virus has not been found

in live wild birds; and the virus is deadly to wild birds.

 

They insist that the virus has spread primarily through the trade in

infected poultry and poultry products, contaminated vehicles or cages,

the use of infected poultry manure as fertiliser and feed, and the

trade in caged wild birds.

 

World avian authority Birdlife International argues that the outbreaks

so far do not follow the route of bird migrations. It says if wild

birds were spreading the virus across continents, there would have

been trails of dead birds along their flypaths. This is not the case.

On the contrary, countries on flight paths of Asian migratory birds

such as Taiwan, the Philippines and Australia, remain flu-free.

 

Towards the end of 2005, millions of wild birds flew to their

wintering sites across Asia, Africa, Europe and the Americas without

the widely predicted outbreaks of H5N1 bird flu associated with their

migration routes.

 

" The most obvious explanation is that migrating wild birds are not

spreading the disease, " says BirdLife International director Dr

Michael Rands in a statement.

 

Migratory birds are also not to blame for the recent cases in Perak

and Penang, says Malaysian Nature Society executive director Dr Loh

Chi Leong. " The migratory birds have wintered for several months in

Indonesia and Australia, and there are no birds dying there. We are

already at the tail end of the spring migration. If wild birds are

infected, they would have showed up earlier. "

 

Loh also says wild ducks and geese, the common hosts of bird flu

viruses, are either uncommon migrants or not found here. Of the 192

species of wild birds which migrate through Malaysia, only seven are

ducks. Geese and swans do not winter here. Most of our migratory

species are shorebirds found mostly on coastal estuaries and mudflats,

away from farms.

 

The case against migratory birds crumbles even further when one

considers that thousands of live wild and migratory birds, including

those in Malaysia, have tested negative for H5N1. Birds which tested

positive were either sick or dead. And dead ducks don't fly.

 

The evidence so far is weighed towards wild birds catching the virus

from infected domestic poultry. The Food and Agriculture Organisation

(FAO) says all of the H5N1 viruses isolated from wild birds during the

2003 and 2004 outbreaks were from dead or dying birds found in the

vicinity of infected poultry flocks or contaminated premises.

 

It is the same scenario here. The infected areas in Perak, although

within the haunts of migratory birds, are also near duck farms.

Ornithologist Lim Kim Chye, who helped set up the Kinta Nature Park,

says the dead cattle egret found in Ipoh could have come into contact

with infected poultry as both wild and farmed birds often mingle and

feed in the same ponds.

 

" The authorities should not allow duck farms near concentrations of

wild birds. It is bad for both, " says Lim. The World Health

Organisation (WHO) has found that domestic ducks act as reservoirs of

the virus; they carry the virus without showing signs of illness.

 

Also alarming, and needing closer investigation, is the widespread use

of poultry manure as food and fertiliser in agriculture and fish

farming. Infected birds can excrete virus particles in their faeces.

WHO says H5N1 virus can survive in bird faeces for at least 35 days at

low temperature (4°C). At a much higher temperature (37°C), it has

survived in faecal samples for six days.

 

Birdlife International believes mute swans in Eastern Europe became

infected when grazing on fields as poultry manure is widely used as

fertiliser there. FAO recommends a ban feeding of poultry manure in

countries affected by or at risk from bird flu.

 

As H5N1 continues to spread, there is a need for responses to be calm,

prompt and effective. Several global bodies say culling migratory wild

birds is misguided and will do more harm than good, not to mention

imperil endangered species. WHO and FAO say culling could simply

scatter the virus more widely by driving flocks away from their normal

routes.

 

Glenda Noramly of the Malaysian Bird Conservation Council fears that

singling out wild birds will divert attention from other ways of

combating the bird flu. " The consequence of just focusing on birds can

be disastrous as the real source of the problem will not be dealt

with, " she says.

 

MNS's Loh says to check the spread of H5N1, actions should target the

known transmission routes: clamp down on movement of infected poultry

and poultry products from infected areas; increase surveillance and

testing of poultry; regulate the use of poultry manure in agriculture;

and stamp the trade in captive birds.

 

But gaps remain in knowledge about H5N1 in wild birds. Scientists

still do not know how wild birds contract the infection, how long the

incubation period is, how easily infected wild birds can transmit the

virus, how ill it makes them and which species are affected. Such

knowledge can help predict and control the spread of H5N1 should

migrant birds be found to carry it in the future.

 

David Li, bird conservation officer of Wetlands International, urges

for regular surveillance of important wetland sites and for wild bird

deaths.

 

" We need more work to see how and why the bird flu happen so we can

make better decisions rather than just blaming migratory birds. "

 

Sources: WHO, FAO and Birdlife International.