Monday, February 23, 2004

A strain of avian flu found on a Texas chicken farm Friday is far deadlier to poultry than originally thought and has spread to two bird markets in Houston, federal officials said yesterday.

However, the bird flu is not the same strain that has killed at least 22 persons in Asia, said U.S. Agriculture Department Chief Veterinarian Dr. Ron DeHaven.

Preliminary tests on the H5N2-type strain found at a farm in Gonzales County, 50 miles east of San Antonio, show that it has a higher mortality rate among birds and is possibly infectious to humans.

Other tests are still pending and may show the virus is a milder version, Dr. DeHaven said.

“We simply don’t know, as we’re very early in that level of testing,” he said in a conference call yesterday.

The Texas outbreak is the first case of the highly pathogenic virus in the United States since an outbreak from 1983 to 1984 that killed 17 million chickens in Virginia and Pennsylvania.

There have been no known human deaths from avian influenza in the United States, said Dr. Nancy Cox, chief of the influenza branch at the Centers for Disease Control and Prevention.

Other low-pathogenic strains, which are not harmful to humans, began surfacing last month at farms and live-bird markets in Delaware, Pennsylvania and New Jersey.

Dr. Cox said the CDC is monitoring an undisclosed number of people that have come in contact with diseased birds at the Texas farm and markets, where live birds are sold for consumption.

The source for this more virulent strain is unknown. Some 6,600 chickens at the Texas farm were destroyed over the weekend. State officials are conducting tests on other locations within a 10-mile radius of the infected farm.

“We presently have no evidence of any human health implications of this high-path virus in Texas,” Dr. DeHaven said, adding that the agency has already taken the preventive step of killing the infected chickens.

The news is expected to further upset U.S. chicken exports, which account for about 20 percent of total U.S. chicken production.

So far, Argentina, Brazil, China, India, Indonesia, Japan, South Korea and Poland have banned U.S. chicken products since the discovery of the mild bird flu in Delaware. Russia, the nation’s largest chicken customer, has suspended chicken imports from Delaware and Texas.

Shares of several U.S. chicken companies, including Tyson Foods Inc., Pilgrim’s Pride Corp. and Sanderson Farms Inc. fell after the disclosure.

Testing began Feb. 17 at the Texas farm, which officials would not name. Those samples tested positive for the H5 virus and additional testing was done to determine its pathogenicity.

“And again, that pathogenicity relates to [the virus’] ability to cause disease and mortality in birds,” Dr. DeHaven said.

The USDA used DNA sequencing and officials confirmed the H5N2 high-path type at 2 a.m. yesterday morning.

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