Washington ? In what could be a devastating blow to America’s beef industry, federal authorities said Tuesday their tests had found the first-ever case of mad cow disease in the United States in a dairy cow from rural Washington state.

The deadly brain-wasting disease ravaged parts of the European agriculture industry in the 1990s.

Its discovery immediately halted U.S. sales of beef to some nations, pressured share prices of fast-food companies and raised consumer concerns about food safety — especially as officials said meat from the cow may have been eaten as hamburgers.

Meat from the animal, which was slaughtered on Dec. 9, traveled through three separate processing plants before a test first revealed the problem 12 days later, but officials at the U.S. Department of Agriculture insisted infectious portions of the animal were removed at the slaughterhouse and diverted to a rendering plant.

“We believe the risk of any human health effects is very low,” Agriculture Secretary Ann Veneman told a hastily convened news conference. “We remain confident in the safety of our food supply.”

Economic impacts

In the first of what may be the first of a cascade of blows to the industry, however, Japan, the largest foreign customer for American beef, announced a temporary halt on U.S. beef imports, as did South Korea. And analysts predicted beef and grain prices would plummet when trading resumes today.

The farm near Yakima, Wash., where the cow originated has been quarantined as officials trace how the animal contracted the disease and where its meat went.

Infected tissue samples from the cow were flown on a military plane to England, where a laboratory in Weybridge is expected to conduct a final set of confirmatory tests. Results are expected in three to five days.

Agriculture officials said they had informed their counterparts in Mexico and Canada, but knew of no immediate plans to close borders to the transport of cattle products. The U.S. beef industry slaughters some 40 million animals every year and is worth $175 billion.

In Europe, Canada

Mad cow disease, known also as bovine spongiform encephalopathy, eats holes in the brains of cattle. It sprang up in Britain in 1986 and spread through countries in Europe and Asia, prompting massive destruction of herds and decimating the European beef industry.

A form of mad cow disease can be contracted by humans if they eat infected beef or nerve tissue, and possibly through blood transfusions. The human form of mad cow disease so far has killed 153 people in Britain and 10 elsewhere, none in the United States. Blood donors possibly at risk for the disease are banned from giving.

In May, Canadian authorities discovered a case of mad cow in an animal in Alberta, leading the United States and a number of other nations to suspend imports of Canadian beef. USDA officials said they were investigating whether the two cases might be linked.

Industry response

Wary of the potential economic impact on their American market, beef producers quickly sought Tuesday to reassure consumers that infected meat wouldn’t reach their tables. “There is no risk to consumers based upon the product that came from this animal,” said Terry Stokes, chief executive of the National Cattlemen’s Beef Assn.

Nevertheless, the impact of the Washington state case could be far-reaching, potentially affecting sales at fast food spots and upscale steakhouses alike, as well as exports abroad.

Investors quickly sent stocks of fast-food hamburger chains falling in after-hours trading Tuesday.

Shares of McDonald’s Corp., the largest fast-food hamburger chain, dropped as much as 4 percent to $24.20. In a statement Tuesday night, McDonald’s spokeswoman Lisa Howard said the company’s supply was entirely separate from the reported case of mad cow disease.

“The meat packer in question has no connection whatsoever to McDonald’s supply chain,” Howard said.

McDonald’s has been through such an event before. When mad cow disease broke out in Europe and Japan, McDonald’s, which has restaurants across the globe, saw significant drops in sales, though its beef was never found to have the disease.

Among other big losers in after hours trading were Wendy’s International Inc., down 2.7 percent, and Lone Star Steakhouse, off 9 percent. Wendy’s did not return calls for comment, nor did Tyson Foods Inc., the world largest meat processor, whose stock fell modestly.

Ironically, the beef industry has been enjoying several years of growing consumption and higher prices, which some experts attribute to the popularity of the meat-centered Atkins diet.

“In the last three years we’ve seen a significant increase in beef demand and consumption,” said John Nalivka, a consultant to the cattle industry. But that could change quickly if mad cow disease is in fact present in a U.S. livestock operation.

“I’m not going to play it down,” he said. “It’s obviously a concern.”

Not terrorist-related

Veneman assured Americans the nation’s food-screening system worked, and no foul play was suspected. “This incident is not terrorist-related,” she said. “I cannot stress this point strongly enough.”

President Bush was briefed a few times on the development Tuesday and was confident Veneman’s department was handling the matter properly, the White House said.

With an election year approaching, the news concerned some in Congress. Rep. Tim Holden, D-Pa., a member of the House Agriculture Committee, said he expected lawmakers to conduct hearings when they return to Washington in late January.

“We’re going to look into this and see the possibility of how this happened,” Holden said. “I’m sure there will be extensive oversight hearings to see what we can do to assure the American people the safety of the food chain.”

Confirmation sought

Veneman said the Holstein, which could not move on its own, was found at a farm in Mabton, Wash., about 40 miles southeast of Yakima. It was flagged as a “downer” animal, meaning it was unable to walk. A federal surveillance program for mad cow disease mandates that such animals be segregated for special treatment as potentially ill.

Parts of the cow that would be infected — the brain, the spinal cord and the lower part of the small intestine — were removed for testing.

But the tests suggesting the animal had the disease did not come back until Monday and Tuesday. In the meantime, the animal’s carcass had been sent to a deboning facility and by Dec. 11 had gone to two other plants for further processing.

Agriculture officials said they presumed the meat was intended for human consumption.

Elsa Murano, undersecretary for food safety at the Agriculture Department, said it was possible the meat had already made it to grocery stores.

Veneman emphasized the brain and spinal tissue did not enter the food supply, though USDA officials are still trying to determine if muscle cuts from the animal were eaten by humans. The distinction is crucial, she said, because mad cow disease is believed to be spread by eating neural tissue, not muscle cuts, from diseased cows.

In England, the disease outbreak was triggered when brain tissue from infected animals was fed to other cattle. Safety measures already in place in the United States prevent that practice.

Veneman said consumers could get daily updates by reading the department’s Web site or by calling 1-866-4USDACO.

Veneman said the Agriculture Department has had safeguards in place since 1990 to check for mad cow disease and 20,526 cows had been tested this year in the United States.

“This is a clear indication that our surveillance and detection program is working,” she said. “We see no reason for people to alter their eating habits … I plan to serve beef for my Christmas dinner.”

But Rep. Gary Ackerman, D-N.Y., said “downer” cows shouldn’t be in the food supply in the first place. The Senate passed such a ban earlier this year, but it failed to make it through the House.

“I blame it on greed, greed, greed,” Ackerman said. “The greed of the industry, the greed of the lobbyists and the greed of the members of Congress.”