Don’t blame the birds, experts say

  • This topic is empty.
Viewing 1 post (of 1 total)
  • Author
  • #3241
    Martin W
    Don’t blame the birds, experts say as FAO warns migrations spread avian flu (Pandemic-Birds)
    Sep 05 14:52 – CP – The Canadian Press

    By Helen Branswell

    TORONTO (CP) _ The UN’s Food and Agriculture Organization renewed
    its warning Monday that migratory birds may be culprits in both the
    spread of avian influenza and threats to future geographic expansion
    of the deadly H5N1 strain.

    But many wildlife authorities and avian influenza experts
    question the contention, saying wild waterfowl may play a
    significantly smaller role in the spread of the virus than the
    Rome-based agency and others suggest.

    Don’t be too quick to blame the birds, these experts warn.

    They believe that feet and wheels, not wings, are behind the
    spread of the virus that has ravaged poultry flocks in Southeast
    Asia since at least late 2003 and was recently found in eastern
    Russia, Mongolia and Kazakhstan.

    “My best guess is probably related to my experience, which is
    (that) humans account for more spread of influenza to domestic birds
    than wild birds do” says Dr. David Halvorson, an avian flu
    specialist at the University of Minnesota. Halvorson and others
    believe that in many of the recent cases where wild birds were
    blamed for H5N1 outbreaks in domestic poultry, the migratory birds
    may actually be victims, not villains.

    “They’re the sentinels. They’re not the reservoir that’s
    spreading it around. They’re infected because the poultry are
    infected,” explains Dr. David Swayne, director of the U.S.
    Department of Agriculture’s poultry research laboratory in Athens,
    Ga., that agency’s main centre for the study of avian influenza.

    An example may be the large die-off of wild birds at the Qinghai
    Lake reserve in western China earlier this year. As many as 6,000
    birds were reported to have died; a number tested positive for the
    H5N1 virus. Molecular analysis of the viruses suggested the birds
    were likely infected by poultry in southern China.

    Those who question the role of the migratory birds say they are a
    convenient scapegoat.

    It’s less embarrassing for a government to blame wild birds than
    to admit that its customs officers are turning a blind eye while
    farmers cross borders to unload infected chickens on unwitting
    buyers or as people smuggle sick fighting cocks to lucrative

    It’s easier to blame a wild bird than to admit live poultry
    markets are serving as petri dishes, with infected birds passing the
    virus to uninfected ones which then transport it to previously
    untouched farms kilometres away.

    “When you have an outbreak, sometimes you don’t really know what
    the cause was,” Swayne says.

    “Nobody going to be upset with you if you say wild birds.”

    He believes the recent die-off of migratory birds in Mongolia, in
    an area where domestic poultry is not found, represents the
    strongest case to date that wild birds may be capable of
    transporting the virus over long distances.

    Even at that, he and others think too little is known about how
    many healthy birds are carrying it, how long they remain infected
    and how long they shed virus to make assumptions about their ability
    to take H5N1 to far-flung destinations such as the Indian
    subcontinent, Europe and Africa, as the FAO has predicted.

    “Those are critical pieces of data that you need before you can
    really strongly make a claim that it’s coming, for sure,” Swayne

    But the FAO’s chief veterinary officer says the danger posed by
    further spread of H5N1 means authorities have to assume migratory
    birds are a risk and do everything possible to prevent wild water
    birds from mixing with domestic poultry flocks.

    “Whatever you think about the scientific certitude _ and we are
    the first saying that there is a need to do a lot of investigation
    because there are too many grey areas _ we cannot, and the countries
    cannot, take the risk they don’t play a role,” Dr. Joseph Domenech
    says from Rome.

    “Saying there is no risk is irresponsible.”

    Domenech admits there is no smoking gun with which to indict
    migratory birds. But he argues the explosion of avian influenza in
    late 2003 and early 2004 _ when nine countries reported near
    simultaneous H5N1 outbreaks _ is suggestive of wild bird spread.
    “It was not possible to explain everything with trade.”

    But Martin Williams counters that if you superimpose the pattern
    of spread over migration patterns, the two don’t mesh.

    “When you looked at it . . . the timings of the migrations and
    the timings of the outbreaks just didn’t fit at all,” says
    Williams, an avid amateur ornithologist from Hong Kong who has been
    studying birds for decades and has taken up the cause of migratory
    birds on his website,

    At the heart of the scepticism about the role of migratory birds
    is the fact that highly pathogenic avian flu viruses _ in other
    words, those that can kill _ until recently were virtually never
    found in wild waterfowl. (From its first recorded appearance in
    southern China in 1996, H5N1 has been a high path virus.)

    Some species of wild water and shore birds are the natural
    reservoir of avian flu viruses. But the viruses they carry are
    invariably of low pathogenicity or “low path” _ they don’t kill
    their hosts.

    When domestic poultry pick up low path viruses from wild birds,
    the viruses can mutate as they cycle through generations of domestic
    birds, ratcheting up pathogenicity in the process. The high path
    offspring can wipe out whole flocks of domestic poultry, but
    typically cannot infect wild birds.

    H5N1 has defied this dogma on several occasions, causing several
    migratory bird die-offs in the wild and infecting and infecting and
    killing ducks in laboratory settings. The only previous time avian
    flu was known to have killed wild water birds was in 1961 in South
    Africa, where there was a die-off of terns.

    Teasing out whether migratory birds are playing a role has been
    made more difficult by the fact that governments haven’t always been
    entirely forthright about the scope, frequency and location of their
    avian flu outbreaks, obscuring patterns which might otherwise come
    into focus.

    “Transparency by some countries of reporting the virus and the
    outbreaks has been a big problem in really trying to figure out
    what’s the real epidemiology and how’s this virus being spread
    around,” Swayne says.

    © 2004 The Canadian Press

    ### End Src CP Id 20050905G1996A Rcvd Sep 05 2005 14:56 ###

    Re Domenech’s comments:
    I’ve seen re foot and mouth disease outbreaks that spread thro UK and to some other places in Europe did not fit all that was known re transport – suggesting that unknown transport happened (as flying wild cows not available as scapegoats).
    Might be irresponsible to say there is zero risk from wild birds spreading bird flu. Irresponsible, too, to overplay the risk.

Viewing 1 post (of 1 total)
  • You must be logged in to reply to this topic.