A rare joint pronouncement from the world’s top health agencies has declared that vaccinating chickens against bird flu would be useful in helping to control the spread of the virulent disease in east Asia.
However, the agencies stopped short of endorsing it as the only way to manage bird flu, saying culling “remains the recommended response” in flocks that have the disease. About 50 million birds have been killed in the epidemic, and at least 16 people. The statement follows an emergency three-day meeting in Rome, Italy, at the headquarters of the UN Food and Agriculture Organization. The FAO was joined by the World Health Organization, and the World Organisation for Animal Health.”The epidemic has not been brought under control and we need an urgent response,” said FAO director general Jacques Diouf.
Klaus Stöhr, head of the Global Influenza Programme at the WHO, said: “This outbreak is completely without precedent. This has to be worked out on a country by country basis.”
Stamping out
Veterinary experts have traditionally regarded the culling of infected livestock, and animals living nearby, as the only effective way to halt the spread of a highly contagious disease. Such “stamping out” was used to control foot and mouth disease in Britain in 2001.
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But Indonesia, after admitting in January that bird flu had been spreading in the country since August 2003, declared that it would manage the disease with vaccination alone, because it could not afford the loss to its farmers. After being criticised for this at a regional meeting last week in Bangkok, it said it would cull as well.
The three agencies struck a compromise in Rome. “Culling infected flocks remains the recommended response when the disease is detected,” said Joseph Domenech, chief of FAO’s animal health service. But vaccination of healthy flocks outside the affected area can help, he said, if the movement of potentially infected animals is also controlled.
Dangerous hybrid
China, one of the 10 countries affected, is culling all poultry within three kilometres of outbreaks, and vaccinating all remaining poultry within five kilometres. South Korea, which seemed to have its bird flu epidemic under control, reported two outbreaks on Thursday on farms eight kilometres away from the last one affected, in January.
Health officials fear that people infected simultaneously with bird and human flu viruses could generate a dangerous hybrid that could sweep the planet.
Vaccinating healthy chickens during an epidemic might reduce the amount of virus to which people are exposed, said Stöhr. This is because even if they become infected, such birds multiply the virus a thousand times less than an unvaccinated flock.
If such birds are infected, they can still spread the virus without appearing sick. Therefore vaccinating birds when there is no known outbreak, as a routine preventive measure, can be problematic.
