Vaccine use urged to stop bird flu

By LAWRENCE K. ALTMAN New York Times

Monday, August 2, 2004

Bangkok, Thailand -- The U.N. Food and Agricultural Organization will issue new guidelines urging wider use of a vaccine for birds to help stop the continuing spread of a virus that is deadly to birds and a threat to human health, an agency official said here last week.

The guidelines, to be issued by the end of August, are needed because new findings show that a strain of the avian influenza virus has become a permanent fixture in many Asian countries, said Joseph Domenech, chief of the organization's FAO animal health services.

Scientists have recently found that the strain of the avian influenza virus, known as A(H5N1), seems firmly rooted among domesticated ducks and wildlife and so cannot be wiped out by culling, quarantines and other standard measures alone, Domenech said. He spoke at a meeting attended by health officials from 10 Asian countries that the FAO convened in part to deal with a resurgence of avian influenza in China, Thailand and Vietnam and the virus' continuing spread in Indonesia.

An estimated 200 million birds have died from A(H5N1) or culling since early this year when the strain simultaneously appeared in eight Asian countries. The scale of the epidemic of an avian influenza virus geographically, economically and socially is "unprecedented," U.N. officials said.

The strain has caused widespread economic havoc to the Thai poultry industry, the world's fourth-largest exporter of poultry products, and has been costly to the economic and nutritional well- being of many poor people who are reliant on raising their own chickens.

At the same time, many influenza experts and public health officials fear a scenario in which an individual becomes infected with both the A(H5N1) avian virus and a human influenza virus. Under such circumstances, the viruses could swap genes to create a new virus to cause a global epidemic that would be difficult to control.

So far the human toll has been small but significant. No human cases have resulted from the most recent outbreaks in July. But earlier in the year, A(H5N1) infected 35 humans in Vietnam and Thailand, killing 24 of them. There has been no secondary spread from person to person.

In the A(H5N1) epidemic in Southeast Asia, health workers are dealing with a situation that differs significantly from outbreaks of other strains of avian influenza. Those outbreaks, in developed countries in temperate regions, have been stopped by using vaccines as a short-term emergency measure in tandem with culling and other standard measures, said Mike Nunn, who manages Australia's Animal Health Science department, and Sarah Kahn, an Australian veterinary consultant to the Food and Agricultural Organization.

In February, the FAO, along with the World Health Organization and the World Health Organization for Animals, said countries affected by A(H5N1) should consider vaccinations as one measure of stopping its spread.

That recommendation was not as strong as the one expected in the new guidelines because last winter many experts and some countries believed they could eradicate A(H5N1) by culling, making vaccination unnecessary, Domenech said.

Now "we must reassess what we are doing" because it is clear that the virus cannot be eradicated, given its presence in ducks and wildlife, Domenech said.

Vaccinations will still be viewed as an adjunct to standard control measures; veterinary health workers will be required to monitor the effects on birds, animals and people. Each country will decide whether to vaccinate.

The vaccines may be appropriate for villages in some countries but not in others, Domenech said.

The vaccines, however, are not magic bullets. Each dose costs about 5 cents, and each bird may need up to three doses. Because the vaccines must be injected, the major cost is from administering them. Participants stressed the urgent need for a vaccine that birds and animals can swallow.

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