Avian flu and wild birds

Qinghai province outbreak, May 2005

Tests confirmed that 178 Bar-headed Geese found dead on a nature reserve in Qinghai province, China, had been infected with the H5N1 bird flu virus, China's official media reported (22 May 2005). Although the geese died shortly after completing their arduous trans-Himalayan migration, scientists consider it more likely that they didn’t bring the deadly H5N1 strain of the virus with them from their wintering grounds, but contracted it locally.

The Chinese authorities introduced measures include banning people from habitats of migratory birds, immunising poultry raised near habitats and routes of migratory birds, and introducing quarantine measures in Qinghai.

Despite this (and previous earlier stories such as storks in Thailand), current scientific evidence suggest that trade in live poultry, mixing of avian species on farms and at live bird markets, and poor bio-security in poultry production contribute much more to disease spread than wild bird movements, according to Samuel Jutzi, Director of the Animal Production and Health Division of the United Nations Food and Agriculture Organisation (FAO).

Mr Jutzi also re-emphasised that the FAO advises against the destruction of wild birds and their habitats, as such practice is unlikely to contribute significantly to disease control.

The FAO’s Avian Influenza Disease Emergency newsletter (AIDEnews) adds:

"The wild birds from which viruses have been isolated were usually sick or dead, suggesting only limited potential for acting as virus vectors over distance unless subclinical infection was prevalent, which does not seem to be the case…"

"…Thus it seems that the rising incidence and widespread reporting of disease in 2003/4 can be attributed to enhanced spread from existing reservoirs of infection in domestic waterfowl and live bird markets leading to greater environmental contamination." FAO AIDEnews, 15 February 2005

BirdLife believes that it is very unlikely that wild birds are playing a significant part in the spread of Highly Pathogenic Avian Influenza (HPAI) because:

• The outbreaks have not coincided with times of the year when birds undertake long-distance migrations. Scientists monitoring areas which overlap the south and east Asian flyways have found either no evidence of the avian flu virus, or different strains to that involved in the Asian outbreaks
• While it is common for wild birds, particularly waterbirds, to carry mild strains of avian influenza virus, there is little evidence that the new virulent H5N1 strain is affecting wild bird populations, or that wild birds are able to spread this Highly Pathogenic Avian Influenza virus
• A few individual wild birds have been found to be infected with the Highly Pathogenic form of the disease. This has generally been in circumstances which suggest that they have been in contact with infected poultry or poultry waste. When found, such birds have been either dead or dying, and in no condition to fly long distances. One reviewer of the literature says "no one has yet found Z-type H5N1 (the form causing outbreaks in Asia), to my knowledge, in a live wild bird healthy enough to migrate"
• There are no known cases of transmission between wild birds and humans
• The UN’s Food and Agriculture Organisation (FAO) has stated that attempts to destroy wild birds or their habitat will not help to prevent or control avian influenza outbreaks. "Rather, authorities should take action to limit the exposure of farmed chickens and other poultry to wild birds by improving the biosecurity of farming enterprises"

Based on evidence from current and former outbreaks, BirdLife believes that intensive farming practices and inadequate disease reporting and control seem to be the main factors behind the spread of Highly Pathogenic Avian Influenza (HPAI). The solution lies in changing farming, trading and veterinary practices. This is where management measures should continue to be applied.