be unafraid, be very unafraid
from here in Hong Kong, inc based on 2003/04 spread in east Asia, se Asia, looks like poultry trade is h5n1 mover; wild birds victims not vectors
Too bad that it seems even birders in UK not aware of this; tho lately, the message swamped by pundits of doom [esp one Henry Niman, who doesn't seem most reliable source]
I did article on this:
Dead Ducks Don't Fly
seems a similar pattern emerging here - outbreaks not going as predicted with bird migrations (esp as big move in around July, when many bar-headed geese flightless!)
much info here:
H5N1 and migratory birds forum
- more posts welcome
This just in (via Phil Round in Thailand):
20050824.2492
Published Date 24-AUG-2005
Subject PRO/AH/EDR> Avian influenza - Asia (10): migratory birds
AVIAN INFLUENZA - ASIA (10): MIGRATORY BIRDS
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Date: Wed 24 Aug 2005
From: Hon Ip <
[email protected]>
Dead birds don't migrate (re. ProMED 20050822.2475) [cf my "dead ducks don't fly"!
-----------------------------------------------
I am in complete agreement with the anonymous ProMED contributor for the
request for more information on the role of H5N1 and wild birds in the
evolving situation in Asia [see commentary to posting 20050822.2475].
Reports of the role of wild birds as the cause of new bird flu outbreaks
occur almost daily, but at the present time, there is little evidence
available to support such statements. So making that kind of material
available to ProMED readers would be greatly appreciated.
One of the few pieces of published data that addresses the question of H5N1
isolation from wild birds is from the work of colleagues in Hong Kong. H5N1
was isolated from clinically healthy birds in Penfold Park during the 2002
pathogenic [influenza] outbreak in Hong Kong SAR. In addition to the
isolation of H5N1 from sick and dying birds at the park, the virus was
isolated from apparently healthy birds, include 2 Canada geese (_Branta
canadensis_), one bar-headed goose (_Anser indicus_) and 2 other geese of
unspecified Anser species (Ellis et al., 2004. Avian Pathol 33:492-505).
[Initially, the SAR authorities reported to the OIE that the affected
population in the Penford Park included resident waterfowl (ducks, geese,
and swans) and wild little egrets (_Egretta garzetta_); no reference was
made to tests in clinically unaffected birds. See 20030126.0236. - Mod.AS]
It should be noted that, although the Canada goose and the bar-headed goose
are migratory species, these birds were in a captive situation, and so the
question of whether they are capable of migration remains unanswered.
A further point illustrating the lack of data on the role of wild birds in
HPAI H5NA transmission is the outbreak in Novosibirsk, Russia. The source
of the outbreak has been attributed to wild birds. [See 20050725.2150 and
<http://www.oie.int/eng/info/hebdo/aIS_60.htm#Sec4>.] But, in some of the
limited information available on the nature of the Novosibirsk HPAI H5N1
virus, as provided by Russia to OIE [see 20050813.2369 and
<http://www.oie.int/downld/AVIAN%20INFLUENZA/Russia%20HPAI.pdf>], the 4
isolates of H5N1 from domestic poultry in 2 regions of Novosibirsk are
similar, but one sample, which is from a wild duck, clearly has a different
PCR electrophoreogram pattern (Figure 1 in the OIE report). While other
data not included in the report may show that the virus in wild birds is
related to those isolated from affected poultry in the Novosibirsk region,
the available data suggest that such is not the case, and certainly no data
that shows the wild birds were the vector of transmission has been made
available at the present time.
Movement of birds, including annual migration, is only one of several
possible means of dissemination of the HPAI H5N1 virus. In many of the
areas of recent outbreaks, there is a thriving trade of live birds and
poultry products. Some of the areas such as Qinghai in China and Hovsgol,
Mongolia are tourist destinations. There is no evidence of sustained human
to human transmission at the present time. But because the influenza virus
can survive in poultry droppings for up to 2 weeks (Lu et al., 2003. Avian
Dis 47:1015-1021), movement of people and contaminated farm equipment can
rapidly spread the virus from one locale to another. Although much has been
made of the recent pattern of spread as indicative of avian migration, many
ornithologists have indicated that the spread of H5N1 does not fit with
known behavior of the bird species in that area of the world (Butler, D.
2005. Nature: <http://www.nature.com/news/2005/050801/full/050801-1.html>):
It should be noted that the same pattern of spread can just as easily be
seen as from the major routes of human transportation.
--
Hon S. Ip
United States Geological Survey
National Wildlife Health Center
Diagnostic Virology Laboratory
Madison, WI
USA
[Those are valuable observations. Any available data on the detection of
pathogenic H5N1 virus strains in subclinically infected uncaged wild birds
will be appreciated.
Subscribers are referred to a paper by FAO authors, published on 6 Aug 2005
in the Veterinary Record: Sims LD, Domenech J, Benigno C, Kahn S, Kamata A,
Lubroth J, Martin V & Roeder P. (2005) Origin and evolution of highly
pathogenic H5N1 avian influenza in Asia. Vet Rec. 157(6):159-64:
"Abstract: Outbreaks of highly pathogenic avian influenza caused by H5N1
viruses were reported almost simultaneously in 8 neighboring Asian
countries between December 2003 and January 2004, with a 9th reporting in
August 2004, suggesting that the viruses had spread recently and rapidly.
However, they had been detected widely in the region in domestic waterfowl
and terrestrial poultry for several years before this, and the absence of
widespread disease in the region before 2003, apart from localized
outbreaks in the Hong Kong Special Autonomous Region (SAR), is perplexing.
Possible explanations include limited virus excretion by domestic waterfowl
infected with H5N1, the confusion of avian influenza with other serious
endemic diseases, the unsanctioned use of vaccines, and the under-reporting
of disease as a result of limited surveillance. There is some evidence that
the excretion of the viruses by domestic ducks had increased by early 2004,
and there is circumstantial evidence that they can be transmitted by wild
birds. The migratory birds from which viruses have been isolated were
usually sick or dead, suggesting that they would have had limited potential
for carrying the viruses over long distances unless subclinical infections
were prevalent. However, there is strong circumstantial evidence that wild
birds can become infected from domestic poultry and potentially can
exchange viruses when they share the same environment. Nevertheless, there
is little reason to believe that wild birds have played a more significant
role in spreading disease than trade through live bird markets and movement
of domestic waterfowl. Asian H5N1 viruses were 1st detected in domestic
geese in southern China in 1996. By 2000, their host range had extended to
domestic ducks, which played a key role in the genesis of the 2003/04
outbreaks. The epidemic was not due to the introduction and spread of a
single virus but was caused by multiple viruses which were genotypically
linked to the Goose/GD/96 lineage via the hemagglutinin gene. The H5N1
viruses isolated from China, including the Hong Kong SAR, between 1999 and
2004 had a range of genotypes and considerable variability within
genotypes. The rising incidence and widespread reporting of disease in
2003/04 can probably be attributed to the increasing spread of the viruses
from existing reservoirs of infection in domestic waterfowl and live bird
markets leading to greater environmental contamination. When countries in
the region started to report disease in December 2003, others were alerted
to the risk and disease surveillance and reporting improved. The H5N1
viruses have reportedly been eliminated from 3 of the 9 countries that
reported disease in 2003/04, but they could be extremely difficult to
eradicate from the remaining countries, owing to the existence of
populations and, possibly, production and marketing sectors, in which
apparently normal birds harbor the viruses."
During early stages of the outbreak, it was argued that the pattern of
spread strongly suggested that the virus was carried by people smuggling
poultry, a practice reportedly widespread in southeast Asia, rather than by
migratory birds. Though there were reports of mass die-offs of rare birds
in zoos in Thailand, regular monitoring of migratory birds in Thailand did
not reveal the virus. In regions with big outbreaks in poultry, local wild
birds were affected; the question remained as to whether their infection
did not originate from the domestic birds (see item 3 in 20040128.0335).
Useful information on waterbird populations worldwide can be found on the
web-site of Wetland International; the organization has recently published
the drafted 4th edition (2005) of "Waterbird population estimates," which
can be accessed at
<http://www.wetlands.org/pubs&/WPE4draft150705.xls>. - Mod.AS]
[see also:
Avian influenza, migrating birds - Asia 20050812.2354
Avian influenza, migratory birds - Mongolia (02) 20050812.2362
Avian influenza, migratory birds - Mongolia: OIE 20050808.2317
Avian influenza, migratory birds - Mongolia: OIE (03) 20050813.2367
Avian influenza - Asia (06): Mongolia, migratory b... 20050819.2443
Avian influenza - Asia (09): Russia (Siberia), OIE 20050822.2475
Avian influenza, wild waterfowl - China 20050527.1462
Avian influenza, wild waterfowl - China (02): warn... 20050601.1529
Avian influenza, wild waterfowl - China (03) 20050604.1558
Avian influenza, wild waterfowl - China (04): (Xin... 20050622.1743
Avian influenza, wild waterfowl - China (05) 20050628.1828
Avian influenza, wild waterfowl - China (06) 20050629.1833
Avian influenza, wild waterfowl - China (07) 20050702.1872
Avian influenza, wild waterfowl - China (08) 20050707.1922
Avian influenza - Europe (03): migratory birds, no... 20050821.2463
Avian influenza - Russia (Siberia)(13): H5N1, OIE 20050813.2369
Avian influenza - Russia (Siberia)(04): OIE 20050725.2150
2004
----
Avian influenza - Eastern Asia (13) 20040128.0335
2003
----
Avian influenza - China (Hong Kong): OIE (02) 20030126.0236]
....................arn/msp/mpp
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