2 2 月 2006 at 5:08 下午 #3293馬丁參加者
Here’s a letter from veterinarian Les Sims, who has extensive field experience with H5N1 in Asia. As he noted in another thread, “I am a veterinarian, not an ornithologist, and have been closely involved with the avian influenza outbreaks in Asia since 1997, while working for the government in Hong Kong (1993-2002) and subsequently as a veterinary consultant working for FAO in China, Mongolia, Viet Nam, North Korea and Thailand.” – compare this experience with most of the H5N1 pundits, yes, me included. [try googling for ‘sims h5n1’]
Prompted by discovery that a dead magpie robin in Hong Kong had H5N1.
(With thanks to Dr Sims for allowing me to reproduce the letter here.)
Learning to live with H5N1 avian influenza
Once again a single case of infection with H5N1 avian influenza has made the
headlines….. but is this really front-page news?
Hong Kong does not exist in a vacuum. It is an integral, albeit small part
of China, a country in which H5N1 avian influenza viruses still exist. In
the Mainland, the disease is occurring in poultry at the village level
without being diagnosed, as demonstrated by recent cases in which disease in
humans preceded detection in poultry. This is not a reflection on the
endeavour or competence of the national veterinary authorities but a fact of
life in poor rural areas where some 50% of the nation’s poultry are reared
and where there is little or no incentive to report disease. China is
currently undertaking mass vaccination for poultry, presumably because the
authorities believe that the risk of infection in poultry is high.
Hong Kong has done a remarkable job in preventing avian influenza in poultry
in the past 3 years but is going to have to learn to live with the threat of
H5N1 avian influenza for many years to come. Highly pathogenic H5N1 viruses
will not be eradicated from the region until such times as there are major
changes to the way poultry are reared and marketed or unless the viruses
change to a less pathogenic form. The former will involve major social
dislocation, as rearing of scavenging poultry in village households is an
economic necessity providing cheap, high quality protein to people who can
least afford to buy it. Such changes will not occur overnight and who will
pay for such changes? The latter seems unlikely given that the current
strains of H5N1 virus have now been circulating in the region since 2001.
Should Hong Kong continue to import live poultry from the Mainland given
infection is occurring there?
Hong Kong has been a leader in developing one of the world’s first avian
influenza-free poultry compartments in which all suppliers are required to
meet stringent biosecurity and vaccination standards. These reduce the
likelihood of incursion of virus into farms and, if this does happen,
prevents the virus from establishing or spreading.
Stringent testing and
checks along the length of the supply chain ensure that silent infection
with viruses is not occurring and that the necessary measures are being
implemented. This compartmentalised approach to trade in poultry is now
advocated by the World Organisation for Animal Health (OIE). It is a
legitimate way of conducting trade in areas where infection or disease may
still be present outside of a well-defined, infection-free compartment.
However, the security of this compartment should never be taken for granted
and recent calls to ensure proper monitoring of its various components are
reasonable. Everything should be done to ensure that all farms, vehicles,
cages and markets in this compartment are subject to the same rigorous rules
and checks. This is why there is a need for a strong veterinary service
covering farms in both Hong Kong and southern China.
Risks associated with poultry imports over the lunar New Year only increase
if there is a breakdown in this compartment. If new farms are used to supply
additional poultry these must be verified as meeting all requirements.
This disease-free compartment will need to be maintained regardless of
whether poultry are sold in markets or are processed at central slaughtering
At present, the public is receiving very mixed messages about avian
influenza and much of this is occurring because of the hype generated by the
media and some sectors of the professional community. There is a huge gap in
the wider community between the perceived and real risk of being infected
with avian influenza viruses. People in many countries are avoiding
consumption of cooked poultry through misplaced fears and some are even
putting off travel to Asia because of perceived risks.
It is still not widely appreciated that there have been millions of
exposures of people to infected poultry in Asia yet relatively few cases of
disease, demonstrating the low level risk of direct spread of avian
influenza from birds to humans. There is also confusion between this direct
spread of virus from poultry with the emergence of a pandemic strain, which
requires evolution of a virus capable of sustained human-to-human transfer.
The probability of an avian influenza pandemic strain of virus arising in
Hong Kong is extremely remote but preparations should continue for the
import of a pandemic strain of influenza virus from elsewhere at some
unknown time in the future. Such a strain will be introduced by people not
Dead wild birds positive for highly pathogenic H5N1 avian influenza viruses
have been found in Hong Kong intermittently in the past and will continue to
be found. The risk to public health has not increased as a result of
detection of virus in a wild bird. All it does is to demonstrate why Hong
Kong’s avian influenza surveillance system is held is such high regard
internationally and is a timely reminder to the poultry industry to ensure
that biosecurity, hygiene and vaccination coverage are maintained.
Detection of a single H5N1-positive oriental magpie robin should not be
front-page news in a region where H5N1 viruses continue to circulate and
reconfirms the “celebrity-status” that these viruses have acquired.
Asia Pacific Veterinary Information Services Pty Ltd
PO Box 353
Post edited by: martin, at: 2006/02/09 13:21