Wild bird role in flu ‘unclear’

The role of swans and other wild birds in spreading bird flu is still unclear and uncertain, according to scientists. Many of the assumptions being made about the part played in the spread of the disease by wild birds simply do not stand up to analysis, they say. International researchers are in Rome for a two-day conference to discuss the spread of avian flu. The scientific meeting has been organised by the Food and Agriculture Organization (FAO) of the UN and the World Animal Health Organization (OIE).

Dr Ian Brown, from the Veterinary Laboratories Agency (VLA) at Weybridge in Surrey, UK, told the BBC News website: “We shouldn’t just assume that it’s a few species of ducks and the swans that are the risk species. Certainly, we have to look at those, but we need to keep a broad open mind on this one.” Dr Brown said that swans were interesting indicators of the presence of the disease, but their role in spreading it was less clear. This is something we may have here for many years and we may have to live with it.

Dr Domenech, FAO, said: “We have to be careful that just because we see dead swans and we find the virus in them that they’re the answer to why the virus is spreading,” he said. “We do know that swans are largely immobile; they don’t migrate over large distances on the whole. “The movements that have happened in Europe in the past six months have been because of bad weather; so we have to be careful that all the explanations of how the virus is spreading are not placed at the swans’ door. They’re one part of a complicated web.” The scientists also heard an impassioned plea for the use of vaccines to control the disease in domestic poultry.

Dr Robert Webster, from St Jude’s Children’s Research Hospital in Memphis, Tennessee, US, said that it was absurd that vaccines were not used. “The global poultry industry is the main spreader of H5N1, but migratory birds have certainly played a role. A main issue in my mind is the use of vaccines at agricultural level to control this thing,” he said. “There are good vaccines available; it can be controlled at source, but the agricultural authorities of the world won’t standardise their vaccines for antigen content. They say it can’t be done, but it’s not true; it can be done.” Dr Webster said that using vaccines was of far greater importance in the developing world. “The wealthy countries can afford to cull their infected birds; the poorer simply can’t. The science allows us to make superb vaccines for poultry – let’s use them for God’s sake.”

There were also calls for a greater focus on Africa. According to the chief veterinary officer of the FAO, Dr Joseph Domenech, if the disease becomes endemic on the continent, it could re-infect the rest of the world for years to come. Dr Domenech said in Africa, “we have a risk of permanent endemicity, we have a risk of new countries being contaminated, and there is a danger of permanent re-infection of other regions through wild birds or trade. In other countries, the efforts are already done; but not in Africa”. Eight African countries have reported outbreaks of bird flu to date but experts speaking here expect that number to rise.

Scientists are questioning if African countries have the economic or political capacity to eradicate the virus. There are worries about the difficulties in enforcing culling and the control of poultry movements, and there are simply not enough staff to carry out adequate monitoring. According to Dr Domenech, Asia and Europe had made progress in the speed of their detection and response. This was the key to dealing with new outbreaks, he said. “Even if there are reservoirs of infection in the world that you can do nothing about, with effective monitoring and response you can control it,” he added. “This is something we may have here for many years and we may have to live with it.” Many delegates spoke of the need for better information to help target their research. There is a growing understanding that while there is excellent research being done on the ground with wild birds, there is a lack of a global perspective.

BBC News
June 20, 2006

Original web page at BBC News