The
Scientist - 28th February 2006
In
a recent news story,
Alex
Kaat with Wetlands
International (WI) seems awfully sure that wild birds didn't
bring avian flu to Nigeria and won't spread it from there to Europe. So,
scientifically, why is he so sure it won't spread to Europe via the ducks? Do
they not fly from Africa back to Europe? From my understanding,
many
wild water fowl -- especially ducks -- show few if any signs of avian flu
infection and spread the virus via their feces, which can be dropped en route
onto non-wetland areas. In fact, in Eurasia, avian flu is spread via wild
birds. Are
WI or any of their partners testing
the Nigeria/African ducks in any numbers to see if the population is harboring
the virus? Are they only testing the birds that drop dead
(i.e. swans in Italy and Greece) and not living populations of other
birds/waterfowl?
Alex Avery
Director of Research Center for Global
Food Issues, Hudson Institute PO Box 202,
Churchville, VA 24421 540)
337-6354, or -6387
[EMAIL PROTECTED]
Alex Kaat responds:
Alex Avery thinks that I am "awfully sure" about
wild birds not being vectors of avian flu, but the language I used is rather
cautious. Expressions used include "unlikely", "don't think", "more likely", "we
think it is more likely" and "there is a risk". Nobody
yet knows the factors responsible for carrying avian influenza to
Africa,
and Wetlands International aims to make this clear in the information it
provides. Too
many people seem to be sure about the role of wild birds. I expressed the
opinion that it is "unlikely" that migratory birds brought the disease to
Nigeria,
but I also named the species most likely to be responsible if this were the
case, and explained that while the northward migration to Europe begins in late
February, it will "most likely" not bring the disease to
Europe.
Reporting of recent outbreaks of HPAI has often been unbalanced and
sensational and
there is a strong
tendency to blame migrating waterbirds while disregarding the role played by
activities related to the poultry farming and transport industries.
In
intensively farmed poultry, the high density of birds and constant exposure to
faeces, saliva and other secretions provide ideal conditions for the
replication, mutation, recombination and selection through which highly lethal
forms can evolve.
The
global nature of the poultry industry, and the international movement of live
poultry and poultry products also provide a likely mechanism for the spread of
the virus
between
Asia, Africa and Europe, and at a local level within these
continents.
The view that poultry movements have
played a major role in the spread of the disease is supported by an
analysis of viral
strains
recently published in the Proceedings of the
National Academy of Sciences.
Some
of the agencies attempting to monitor and control avian flu, such as the FAO,
seem to have been reluctant to draw attention to the role of intensive
agriculture, because of the impact on national economies and on access to cheap
sources of protein. There are also powerful vested interests in the
global poultry industry. It is noteworthy that countries
such as Japan and South Korea, which imposed strict controls on the import and
movement of domestic poultry after initial outbreaks, have suffered no further
infections.
If wild birds had been spreading the
disease across continents it would be reasonable to expect trails of outbreaks
following migration routes, but this hasn't happened.
Highly pathogenic
avian influenza viruses are very rare in wild birds. Our ongoing
work in Africa will help answer Alex Avery's question about whether African
populations of waterbirds are harbouring the virus or not.
Alex Kaat
-Wetlands International
[EMAIL PROTECTED]
Links within this article
S. Pincock, "Fears of Africa flu spread," The Scientist, February 14, 2006.
http://www.the-scientist.com/news/display/23120/
H. Chen et al, "Establishment of multiple sublineages of H5N1 influenza
virus in Asia: Implications for pandemic control," PNAS, February 10, 2006.
PM_ID: 16473931
