Announcement

Collapse
No announcement yet.

Migration of Whooper Swans and Outbreaks of Highly Pathogenic Avian Influenza H5N1 Virus in Eastern Asia

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Re: Migration of Whooper Swans and Outbreaks of Highly Pathogenic Avian Influenza H5N1 Virus in Eastern Asia

    ...but there are others: Ducks and geese, songbirds and seabirds...They do different things, migrate in different ways, eat and behave differently...
    I've long assumed that much AI transmission wasn't always directly from one species, but rather like the passing of a baton in a relay race. (Dr. Niman's analogy) Even if one species didn't get infected in their breeding area (which is likely as they don't always "mix" much while breeding), their travel companions might be asymptomatic carriers and would pass it to another species (including local wild birds) during a several-day food/rest stop.

    I remember when H5N1 first came to Turkey in 2005/2006. It arrived in some migratory birds that died at a reservoir, then about 3 weeks later local wild birds started dying, then another 3 weeks later local poultry started dying, and about 3 weeks later people started dying. I think it takes some time for an infection to spread enough that there is a higher density of ill birds, thereby creating the circumstances for likely spread to other hosts.

    If those Whooper Swans are like our local Trumpeter Swans, they claim a lake as their exclusive territory during breeding. Other swans might make quick stops during migration, but once breeding has started an established pair will attack other swans. However, during migration they share lakes/ponds/wetlands with other swans and a wide variety of other species. That mix of species can vary during their migration, as there are major "funnels" where there may be a one time mixing with another species.

    Given all the variables in migratory patterns, etc. I'd consider the conclusions from a single-species study to be less reliable than one from a multi-species study.

    .
    "The next major advancement in the health of American people will be determined by what the individual is willing to do for himself"-- John Knowles, Former President of the Rockefeller Foundation

    Comment


    • #17
      Re: Migration of Whooper Swans and Outbreaks of Highly Pathogenic Avian Influenza H5N1 Virus in Eastern Asia

      Originally posted by AlaskaDenise View Post
      I've long assumed that much AI transmission wasn't always directly from one species, but rather like the passing of a baton in a relay race. (Dr. Niman's analogy) Even if one species didn't get infected in their breeding area (which is likely as they don't always "mix" much while breeding), their travel companions might be asymptomatic carriers and would pass it to another species (including local wild birds) during a several-day food/rest stop.

      I remember when H5N1 first came to Turkey in 2005/2006. It arrived in some migratory birds that died at a reservoir, then about 3 weeks later local wild birds started dying, then another 3 weeks later local poultry started dying, and about 3 weeks later people started dying. I think it takes some time for an infection to spread enough that there is a higher density of ill birds, thereby creating the circumstances for likely spread to other hosts.

      If those Whooper Swans are like our local Trumpeter Swans, they claim a lake as their exclusive territory during breeding. Other swans might make quick stops during migration, but once breeding has started an established pair will attack other swans. However, during migration they share lakes/ponds/wetlands with other swans and a wide variety of other species. That mix of species can vary during their migration, as there are major "funnels" where there may be a one time mixing with another species.

      Given all the variables in migratory patterns, etc. I'd consider the conclusions from a single-species study to be less reliable than one from a multi-species study.

      .
      I totally agree with you-that's what I think makes this study interesting. They're basically suggesting that swans are less likely to be involved in long-distance transmission, but that other species are more likely to be the long-distance vectors.

      It would be useful to know which other species are migrating just before/during/after the swans, and to see what the rate of disease transmission is locally from infected swans. For example, perhaps they don't play a huge role in long-distance transmission (as this study suggests), but maybe they are highly contagious once infected, and are actually a very important link in maintaining infection rates across multiple species during migration.

      Dr. Niman brings up the point that outbreaks coincides with arrival of migrating whoopers; nothing he cites precludes the equally likely scenario of them becoming infected upon arrival through contact with other infected species. Which other species were there when they arrived? How long had they been there? What is the phenology of species migrating through Asia? We know very little about these questions, and to say that because the distribution of infected whoopers overlaps with the timing of outbreaks misses the point! It might also correlate well with sunspot activity, etc. Correlation doesn't prove anything--which is why it's important to try to get to the bottom of how H5N1 travels through the environment, where the reservoirs are, how efficiently it's transmitted between species, what the proportion of asymptomatic carriers are, and then overlay that onto breeding/migration phenology, poultry production, climate.

      It's a much more complex equation that would actually give us some ability to predict where outbreaks might arise, prioritize limited resources for biosecurity & wetlands conservation, and to enact preventative measures to help local populations weather the storm...
      Last edited by canagica; June 4, 2009, 09:16 AM. Reason: used wrong pronoun

      Comment

      Working...
      X