birding...

Autumn water bird migration ends without spread of bird flu

As the year draws to a close, millions of wild birds have flown to their wintering sites across, Asia, Africa, Europe and the Americas without the widely predicted outbreaks of H5N1 bird flu associated with their migration routes. [On 28 November, the Dutch agriculture ministry announced it was planning to lift restrictions preventing contact between free-range poultry and migratory birds. "The peak of the bird migration season is finished by mid-December, and also no infected birds have been found in our monitoring of wild birds," the ministry said. This is the first official admission that the bird flu epidemic widely predicted for this autumn and winter, as migratory waterbirds moved south and west into Europe, has not materialised.] "The most obvious explanation is that migrating wild birds are not spreading the disease," said Dr Michael Rands, Director & Chief Executive of BirdLife International.

"Migratory wild birds were blamed for spreading bird flu west from Asia, yet there's been no spread back eastwards, nor to South Asia and Africa this Autumn. The limited outbreaks in eastern Europe are on southerly migration routes but are more likely to be caused by other vectors such as the import of poultry or poultry products. The hypothesis that wild birds are to blame is simply far from proven," said Dr Rands.

[The current series of outbreaks began in 2003 in South-east Asia, where a dramatic increase in intensive poultry production is sometimes combined with poor hygiene and biosecurity in small backyard enterprises. Birds from different areas are brought together in networks of poultry markets, and often transported hundreds of miles. There are at least 144 strains of avian influenza, many of which circulate in wild birds at low levels. Most strains are mild and are designated ‘Low Pathogenicity Avian Influenza’ (LPAI). But a few subtypes can cause massive mortality in poultry and are designated ‘High Pathogenicity Avian Influenza’ (HPAI). Wild birds can also be infected with, and killed by, HPAI viruses. They appear to acquire the virus through contact with infected poultry or with facilities used by them. Subtype H5N1 evolved in poultry from Low Pathogenicity Avian Influenza viruses that were probably acquired from wild birds. Conditions in poultry flocks (such as crowding, and prolonged contact with faeces, saliva and other bodily secretions) keep the viruses circulating as they evolve.]

"Wild birds occasionally come into contact with infected poultry and die: they are the victims not vectors of H5N1 bird flu."

BirdLife maintains that better bio-security is the key to halting the spread of bird flu.

In particular, BirdLife is urging governments and relevant agencies to concentrate their efforts on the poultry and cage bird trades and to impose the following prevention measures:

* Banning the movement of poultry and poultry products from infected areas [Outbreaks in China, Kazakhstan and southern Russia are connected by major road and rail routes. The ‘transmission routes’ between outbreaks in Asia do not follow migratory flyways. Many of these outbreaks also occurred in summer, when birds were moulting and not capable of flight. Live animal markets have played a major part in spreading the virus, and were identified as the source of the HPAI H5N1 infection in chicken farms in Hong Kong in 1997. In Viet Nam, the circulation of HPAI H5N1 in geese in live bird markets in Hanoi was documented three years before the 2004 outbreaks in chicken farms. HPAI H5N1 has been found in duck meat imported from China into South Korea, Japan and Taiwan. Poultry are still being illegally imported from Asia into the USA. In October 2005, 3,000 chickens were intercepted by Italian customs after being smuggled into the country from China, and a major haul of illegally imported Chinese poultry was recently discovered in the UK.]

* Banning the use of untreated poultry faeces as fertiliser and feed in fish-farms and in agriculture [Domestic bird waste is widely used as food and fertiliser in fish farming and in agriculture, yet infected poultry are known to excrete virus particles in their faeces. The use of untreated faeces in fish farming was recently described by the United Nation's Food and Agriculture Organization as a ‘high risk production practice’. Russian fish farms have begun using chicken faeces as fish farm fertiliser, and this practice is employed in Eastern Europe where poultry faeces are also spread onto agricultural land. The Government of Vietnam has warned local residents against the risk of dumping tonnes of chicken faeces into rivers and lakes as fish food; one boy has died of bird flu after swimming in a river where infected chicken carcases were discarded. In October, Mute Swans died at fish farms in Croatia and Romania.]

* Restricting the international movement of captive birds in trade [Customs in Taiwan have intercepted two consignments of infected birds being smuggled from mainland China. In 2004 a pair of Mountain Hawk-eagles smuggled in hand luggage from Thailand to Belgium were found to have the disease, and in the UK recently imported captive birds died of bird flu in quarantine.]

"Implementing measures like these are proven to work," says Dr Rands. "For example, Malaysia and South Korea both experienced bird flu outbreaks through importing infected poultry products, but stamped the disease out and have remained disease free through improved biosecurity. In the mean time, hundreds of thousands of waterbirds have arrived to winter in, or migrated through South Korea, and many migrant waders have passed through Malaysia."

"Better biosecurity is the key to controlling the disease's spread," said Dr Rands. "But the virus can rapidly mutate, so it's important to monitor wild bird populations to look for evidence of new strains arising."

NB Around 16,000 live wild birds all tested negative for the disease in Hong Kong since 1997. Pakistan has tested 700 migratory birds and found no traces of HPAI H5N1. 2,500 migratory shorebirds recently tested in New Zealand and 173 shorebirds tested in Australia were all negative for HPAI H5N1. 20,000 birds (comprising 250 species) in Europe in tests dating back to 1986 (mainly in the Netherlands) all proved negative for HPAI H5N1. "Several thousand birds" tested in Alaska during summer 2005 were all negative for HPAI H5N1. Nine dead Jungle Crows, adjacent to a poultry outbreak in Japan in 2004, tested positive for HPAI H5N1 out of around 5,000 birds tested; the remainder were negative. More than 5,000 waterfowl specimens tested in Korea in 2003-2004 were all negative for HPAI H5N1. One dead Whooper Swan, out of 850 birds tested in Mongolia in August 2005 was positive for HPAI H5N1; the remainder were negative. In Thailand in 2004, HPAI H5N1 was detected in two dead crows at an outbreak site, but 23 live crows and 55 live pigeons at the site where negative. Further testing in the above countries and elsewhere is on-going, but results are not all available currently.

Created: 08th Dec 2005