Don’t blame the birds, experts say

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    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.

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