Role of migratory wild birds and what to do about it (if anything)
The problem of H5N1 virus traveling the globe via migratory birds has been, shall we say, contentious. Because migratory birds have a constituency--birders and ornithologists. Which is a good thing for the birds and ultimately a good thing for flu science. Ultimately. I think the evidence implicating movement of the virus via migratory wild birds is fairly good, maybe even compelling. But I would have to agree there are many major uncertainties as well.
The principal argument of the bird community seems to be that birds sick with avian influenza cannot fly far. But there is also good evidence that the virus is highly pathogenic for some bird species and not others. So this argument isn't persuasive. The argument that if they are truly a source of infection we should see outbreaks throughout their migration paths seems more plausible, but surveillance is not that good in many of these areas, nor do we know the spatial patterns of viral shedding. The fact that outbreaks have occurred where there is no evidence of migratory birds means that either we haven't detected the presence of those birds, or more likely, that there are other ways of spreading the disease, of which spread via wild birds is only one, but an important one for geographic dispersion.
But it is true that there is much to learn, and taking precipitous action in the face of this kind of uncertainty may do more harm--perhaps much more harm--than good. Culling of wild birds or destruction of their natural habitat, as has sometimes been suggested, is neither feasible nor likely to succeed, even if it could be done. What it would almost certainly do, however, is contribute further to the already alarming deterioration of our environment and its biodiversity.
If migratory birds are indeed spreading the virus, as seems likely in some instances, there is not much we can do about it except recognize the importance of surveillance along the migratory pathways and get ready for the consequences. Reform of industrial poultry raising practices and control of indiscriminate spreading of poultry manure also seem like sensible things.
I don't think that wild birds are innocent of spreading this virus and I think denying this is not productive. What we need is some clear thinking about what can and should be done about migratory birds--if anything. It is possible--and I think likely--that this is a variable we cannot control and attempts to do so will turn out to be harmful.
The principal argument of the bird community seems to be that birds sick with avian influenza cannot fly far. But there is also good evidence that the virus is highly pathogenic for some bird species and not others. So this argument isn't persuasive. The argument that if they are truly a source of infection we should see outbreaks throughout their migration paths seems more plausible, but surveillance is not that good in many of these areas, nor do we know the spatial patterns of viral shedding. The fact that outbreaks have occurred where there is no evidence of migratory birds means that either we haven't detected the presence of those birds, or more likely, that there are other ways of spreading the disease, of which spread via wild birds is only one, but an important one for geographic dispersion.
But it is true that there is much to learn, and taking precipitous action in the face of this kind of uncertainty may do more harm--perhaps much more harm--than good. Culling of wild birds or destruction of their natural habitat, as has sometimes been suggested, is neither feasible nor likely to succeed, even if it could be done. What it would almost certainly do, however, is contribute further to the already alarming deterioration of our environment and its biodiversity.
If migratory birds are indeed spreading the virus, as seems likely in some instances, there is not much we can do about it except recognize the importance of surveillance along the migratory pathways and get ready for the consequences. Reform of industrial poultry raising practices and control of indiscriminate spreading of poultry manure also seem like sensible things.
I don't think that wild birds are innocent of spreading this virus and I think denying this is not productive. What we need is some clear thinking about what can and should be done about migratory birds--if anything. It is possible--and I think likely--that this is a variable we cannot control and attempts to do so will turn out to be harmful.
posted by Revere at
12/28/2005 08:19:00 AM
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