Bird Flu Drug Rendered Useless
Saturday, June 18, 2005
HONG KONG -- Chinese farmers, acting with the approval and encouragement of government officials, have tried to suppress major bird flu outbreaks among chickens with an antiviral drug meant for humans, animal health experts said. International researchers now conclude that this is why the drug will no longer protect people in case of a worldwide bird flu epidemic.
China's use of the drug amantadine, which violated international livestock guidelines, was widespread years before China acknowledged any infection of its poultry, according to pharmaceutical company executives and veterinarians.
Since January 2004, avian influenza has spread across nine East Asian countries, devastating poultry flocks and killing at least 54 people in Cambodia, Thailand and Vietnam, but none in China. World Health Organization officials warned the virus could easily undergo genetic changes to create a strain capable of killing tens of millions of people worldwide.
Although China did not report an avian influenza outbreak until February 2004, executives at Chinese pharmaceutical companies and veterinarians said farmers were widely using the drug to control the virus in the late 1990s.
The Chinese Agriculture Ministry approved the production and sale of the drug for use in chickens, according to officials from the Chinese pharmaceutical industry and the government, although such use is barred in the United States and many other countries. Local government veterinary stations instructed Chinese farmers on how to use the drug and at times supplied it, animal health experts said.
Amantadine is one of two types of medication for treating human influenza. But researchers determined last year that the H5N1 bird flu strain circulating in Vietnam and Thailand, the two countries hardest hit by the virus, had become resistant, leaving only an alternative drug that is difficult to produce in large amounts and much less affordable, especially for developing countries in Southeast Asia.
"It's definitely an issue if there's a pandemic. Amantadine is off the table," said Richard Webby, an influenza expert at St. Jude Children's Research Hospital in Memphis.
Health experts outside China previously said they suspected the virus's resistance to the medicine was linked to drug use at poultry farms but were unable to confirm the practice inside the country. Influenza researchers at the U.S. Centers for Disease Control and Prevention, in particular, have collected information about amantadine use from Chinese Web sites but have been frustrated in their efforts to learn more on the ground.
China has previously run afoul of international agencies for its response to public and agricultural health crises, notably the SARS epidemic that began in 2002. China's health minister was fired after the government acknowledged it had covered up the extent of the SARS outbreak by preventing state-run media from reporting about the disease for months and by minimizing its seriousness.
In interviews, executives at Chinese pharmaceutical companies confirmed that the drug had been used since the late 1990s, to treat chickens sickened by bird flu and to prevent healthy ones from catching it.
"Amantadine is widely used in the entire country," said Zhang Libin, head of the veterinary medicine division of Northeast General Pharmaceutical Factory in Shenyang. He added, "Many pharmaceutical factories around China produce amantadine, and farmers can buy it easily in veterinary medicine stores."
Zhang and other animal health experts said the drug was used by small, private farms and larger commercial ones. Amantadine sells for about $10 a pound, a fraction of the drug's cost in Europe and the United States, where its price would be prohibitive for all but human consumption.