Improper poultry raising and sales techniques - rather than the flights of migratory birds - play the most important role in the spread of the deadly H5N1 bird flu virus, United Nations officials said yesterday at a conference in eastern China.

Dr Vincent Martin, an official with the UN's Food and Agriculture Organization, said the spread of bird flu is mainly the result of the world's rapid and unregulated development of animal production to meet the increased demand for protein.

His comments came during an international conference in Nanchang, Jiangxi Province.

Highly concentrated domestic poultry production systems, especially in Asia, are still using centuries-old practices that place humans and poultry in proximity, he said.

Meanwhile, the constantly evolving nature of the virus has provided the ideal conditions for the emergence of new strains of avian influenza.

Evidence indicates wild migratory birds play a minor role in the long-distance spread of the virus, Martin said, adding that the main causes of the deadly disease are the trade in poultry and poultry products.

Marco Barbieri, executive secretary of the Convention on Migratory Species of the UN Environmental Program, said that despite media attention the spread of bird flu is not widely understood.

Misinformation has led to wild birds bearing major blame for transmission of the disease, the official said.

"This creates political pressure for ill-advised and disproportionate policies such as the culling or harassment of wild birds and the destruction of wetland habitats," Barbieri said.

Other modes of transmission, such as the trade in poultry and poultry products, the trade in caged birds and human movements may well play a far more significant role in the spread of bird flu, he said. And in some cases, these pathways have been underestimated and do not receive proportionate media exposure.

"We need to present an accurate and balanced view which acknowledges that there are a number of factors whose relative importance can change, depending on the area or outbreak concerned," Barbieri said.

It is clear that trade in domestic poultry has been a crucial factor, even in transmitting avian influenza across continents, he said.

Numerous species of wild birds, especially water fowl, have been proven to be susceptible to infection by H5N1, however, he pointed out.

Close contact between wild birds and poultry can lead to cross-infection. The loss of wetlands around the globe has forced many wild birds into alternative sites such as farm ponds and paddy fields, bringing them into closer contact with chickens, ducks, geese, and other domestic fowl.