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Tuesday, February 07, 2006

Response to Latest Wild Birds and Bird Flu News

I don't normally have long posts here, but wanted to share the latest thoughts on wild birds and avian influenza from Nial Moores of Birds Korea. This was posted to BirdLife's aiwatch email list this morning, and is a good summary of what we know, and don't know, about the relationship between wild birds and the spread of avian influenza:

It is increasingly apparent that H5N1 avian influenza has now become one of the most immediate threats to wild birds and their conservation in Eurasia. This is not because wild birds yet threaten human health (apparently there is still no case where a wild bird has even been suggested to infect a human with the disease, and more surprisingly it seems there is still not yet a single case where wild birds have even been proven unambiguously to have infected poultry...?). It is rather because of all of the suspicion and villification of wild birds, and because wild birds can be killed by Highly Pathogenic Avian Influenza H5N1: both directly, and through culls.

Very recent so-called response strategies to claims that wild birds are spreading HPAI H5N1 include calls for a massive cull of wild bird in parts of Siberia (including the destruction of nesting habitat), and the callous slaughter of some wild birds left exhausted by severe cold in Romania (they were, according to a January 31st Reuters report, beheaded or used as live footballs by a gang of local men). This in addition to the extraordinarily cruel treatment of poultry in many areas, bagged and burnt to protect our health.

The role of wild birds in the active long-range spread of HPAI H5N1 has been sensationalised and stated as fact ad nauseam for a number of years now it seems, and although the New Scientist article is yet another to suggest such a so-called revelation, it seems appropriate to note its use of the word CAN (rather than the word DO) when suggesting long range spread by wild birds.

Note too, quote:
The researchers analysed samples taken from 13,000 migratory birds and 50,000 market poultry in southeast China between January 2004 and June 2005, when the Chinese government banned independent sampling. In the markets, they found H5N1 in about 2% of apparently healthy ducks and geese, and some chickens, in all but two of the months in the sampling period.
End of quote

The 2% level of infection of apparently healthy poultry was found in markets. Only 6 apparently healthy wild birds out of 13 000 were found infected with H5N1 (though even here the details are left very sparse: which species of waterbird, and at what stage of infection they were at). The short New Scientist article then appears to take two huge leaps in logic, the first in assuming that infected wild birds can migrate long distances just because infected captive juvenile mallards (freed from other stresses) can recover and fly, and second in suggesting that just because the genetic make-up of the virus is similar between infected ducks in Poyang, birds at Qinghai and chickens in Turkey, that this somehow proves the method of spread. This seems especially important when the thrust of the research reveals how widespread the virus has become in poultry in China, and even more significantly how many asymptomatic infected poultry can carry and shed the virus.

Omitted from this and many other similar articles too is a still huge amount of negative data, and numerous unanswered questions, re the spread of HPAI H5N1 by wild birds.

The listserver group AI Watch (orginally set up by some staff in Birdlife, an excellent initiative for which they are to be warmly congratulated) contains as its members many bird conservationists (including those working in areas with outbreaks), and a range of others with H5N1 relevant expertise. Its members have been trying honestly and openly to look at the available evidence - through researching background information to areas with outbreaks, and through applying existing understanding of wild birds and their migrations to the discussion (something by and large sorely lacking so far: really, which wild bird species have a migration route that takes them from southeast China to Qinghai and then onto Europe?).

The following is a personalised summary of a few of the causes so-far suggested by members of the AI watch group as potential/already implicated in the spread of HPAI H5N1 (what a very few of us still stubbornly call Poultry Flu!):

1) Spread by the legal and illegal caged bird trade. Known examples of diseased captive birds with HPAI H5N1 include the parrot in the UK, Hawk-eagles found in baggage in Belgium, mesias in Taiwan, and a captive Flamingo in Kuwait. The first three were detected in customs, preventing further spread of the disease. The last, like several others, was immediately identified by some media as carried by a migratory wild bird - despite overwhelming evidence to the contrary (the flamingo was in a collection on private property apparently). The recent discovery of infected falcons at a falcon centre in Saudi Arabia is yet one more example of this form of spread.

2) The related Merit Release: the purposeful release of once-captive birds into the wild in order to gain spiritual merit. Any increase in reports of infected wild birds after such ceremonies?

3) The movement of poultry and eggs, legal and illegal, and the movement of vehicles and personnel that might also have been contaminated by virus (infected excrement carried on shoes, tires or crates etc). The poultry industry is an enormous industry, legal and illegal, that rears billions of birds annually, moving them both within and beyond national borders: across the width of China, from Thailand to Russia etc. This poultry is of course used for human consumption, and in some cases (as in western China) for control of locust outbreaks, with the potential to infect natural wild bird habitats. Note that this virus can be maintained in the environment for significant periods: apparently for up to two or three weeks in cold water or in droppings.

H5N1 outbreaks in South Korea and Japan a couple of years back were traced back to infected poultry meat imported from China. The outbreaks in both countries were stamped out quickly by controls on imports and culls of infected poultry. Testing of wild birds in both countries at that time and subsequently revealed none (apart from a few dead ones: see below) were infected with H5N1. How could this have been so if large numbers of healthy yet infected wild birds were carrying the virus around, infecting poultry as they went, as apparently suggested by the New Scientist note below?

4) Secondary spread to wild birds by infected poultry, including contamination by such poultry of local environments. The HPAI H5N1 virus killed several non-migratory species like Large-billed Crows in Japan and Eurasian Magpie in Korea - species that scavenge around poultry farms (among other places). This, as well as point 5 below, also seems relevant to discoveries of dead H5N1-infected waterbirds like Chinese Pond Heron, Little Egret and Grey Heron, that often feed in polluted fish-rich waterways (e.g as found in many areas near poultry farms, where waterbodies can be enriched by agricultural run-off).

5) Spread though use of poultry manure as fertiliser in fish-farms. Requiring further investigation, is it not striking that fish-farms using poultry manure enrichment were apparently set up in Qinghai shortly before the massive outbreak there that wiped out several thousand Bar-headed Geese in spring 2005? That species like the Mute Swan, migrating from countries without H5N1 outbreaks, have been found infected at fish-farms in countries with outbreaks?

6) Spread by infected wild birds. The limited, perhaps inter-connected, outbreaks in wild birds in Mongolia in the summer of 2005 seem to suggest that such medium-range spread by wild birds is possible. Considering the rapid spread of outbreaks of H5N1 in poultry in southern Siberia just before, it seems at least possible that a few ducks infected by sick poultry (or their environs) would be able to fly several hundred kms south to Mongolian wetlands where they could then infect a small number of local nesting waterbirds like Whooper Swans before succumbing to the disease. What is equally or even more important (and too rarely mentioned) is that such outbreaks appear to be extremely rare indeed; that in Mongolia they were very limited in scale; and that they petered out quickly. The virus was not maintained in a highly pathogenic state in wild birds in Mongolia; the outbreaks did not lead to known outbreaks in wild birds in neighboring countries; and they did not involve known infection of poultry or humans by wild birds.

While considering the above points, the need to review more of the negative data becomes even clearer:

1) Why have there never been HPAI H5N1 outbreaks in several countries in East Asia that maintain very strict import controls (on poultry and caged birds), even though the same countries receive many wild migrant birds from infected regions annually?

2) IF wild birds are responsible for spreading the virus from Qinghai to Russia and eastern Europe, why have the same species been unable even to reinfect poultry or wild birds in South Korea and Japan (we have well over a million waterbirds coming from Siberia and China to Korea in winter, yet no outbreaks of HPAI H5N1 here for a couple of years)?

3) Why have many species of geese and other waterbird species that breed in genuinely remote areas of northern Siberia etc to winter in infected regions (where they mix with species like Mallard and Pochard, both implicated by some as H5N1 carriers), not yet been infected?

4) Why has the disease not yet spread though Siberian-nesting waterbirds from Asia into the Americas or into Australia or New Zealand (it has now had 10 years in which to do so, while it apparently managed to move from China or SE Asia to western Asia and eastern Europe in only the past 8 months)?

5) Why no outbreaks in India this winter (it was after all infected Bar-headed Geese, that winter in India, that were for a while blamed for spreading the disease north from Qinghai last summer)?

6) Why too do the infected wild bird species seem to keep falling into the same several categories, namely: (a) scavengers around human habitations and poultry farms (crows etc), (b) species popular in capivity (from falcons, to laughing thrushes and Oriental Magpie Robins), and (c) waterbirds that need to use human-modified wetlands?

The pattern of outbreaks, to me at least, seems to vary little. Typically, it involves sick poultry and quick accusations that wild birds infected them; it includes calls for controls on wildlife reservoirs by either media, decision-makers or the general public; and each time it includes papers, notes or skewed media articles revealing that finally there is now overwhelming evidence that wild birds and not people and their poultry are really to blame.

It would be really wonderful if more such questions were asked repeatedly to media and certain leading organisations (like FAO) that have been always been so quick to blame wild birds for outbreaks of the disease.

Contrary to widespread reports, it is not bird conservationists that are burying their heads in the sand...

Many questions (and sadly still far too few people asking them).

With best wishes and birding,

Nial Moores
Birds Korea, South Korea

1 comment:

Anonymous said...

Thanks for posting this. Even birders are saturated with bird flu news, but this is stuff they should be especially aware of.

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