bird flu and migratory birds

Avian flu (H5N1) is spreading from Asia into Europe, and I've heard news reports indicate that the spread is facilitated by migrating birds, bringing it into an area at which time local poultry flocks become infected. Influenza viruses occur naturally in wild birds, especially waterfowl, but the spread of H5N1 does not mirror migratory patterns (it has not shown up in many Asian migratory bird destinations), but instead has followed commercial movements of domestic poultry. Migratory birds may play a small role in transporting the disease, but it is certainly not the slam-dunk explanation offered by most media.

The viruses that are found in wild birds are generally benign.  The highly pathogenic viruses that cause great mortality in domestic poultry flocks are very rare in wild birds. In Asia, domestic poultry flocks are often allowed to mix freely with wild birds, especially waterfowl, which facilitates transmission to migratory waterbirds. There is no evidence that H5N1 infection in humans have been acquired from wild birds.

Two well-respected bird conservation organizations have come out with strong statements warning against the culling of migratory birds: BirdLife International and the American Bird Conservancy.  These statements echo one made last year by the United Nations Food and Agriculture Organization.   

Even if migratory waterfowl were responsible for the spread of H5N1, the draining of wetlands (another alarmist reaction) could exacerbate the spread of the disease by dispersing the birds more widely, and may lead to overcrowding and stress at new gathering areas, making even healthy birds more vulnerable to infection.

Of course, killing migratory birds and draining wetlands would do serious damage to bird populations and biodiversity, and must be avoided.  Nice synopsis of do's and don'ts at How to Save the World.

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Comments

[Rob]

While the direct evidence of wild birds transmitting H5N1 is hard to come by, there is increasing evidence that some wild birds can harbor some strains of H5N1 without showing visible signs of infection--making transmission by wild birds at least theoretically more possible. See the latest reports out of Russia of apparently healthy coots, shorebirds, and several ducks with H5N1. See also the lab tests showing how mallards and domestic ducks can transmit some strains of H5N1 without sign of infection. Links at birdchaser.blogspot.com.

[thebhc]

Hi,

Just saw your piece here. For further info about the bird flu hysteria, I have put up a review of the media, etc. over at The Bonehead Compendium. This may not be quite up your alley, but I was interested to see your remarks about the media hyping the migratory bird angle.

Flipping the Bird.
http://www.boneheadcompendium.com/mod/columns/display/75/index.php

cheers,

ken