Washington, Dec. 30 (Reuters): The Bush administration faced growing political pressure over America’s first case of mad cow disease today after some opposition Democrats urged it to ban sick cattle from the human food supply.

More than two dozen countries stopped buying US beef since the first case was diagnosed last week in a sick cow sent to slaughter in Washington state, bringing the $3.2-billion US beef export business to a halt.

With the Republican Bush seeking a second four-year term next year, two Democratic lawmakers yesterday backed a Senate proposal to safeguard against the spread of the disease by banning US“downer” cattle, those too sick or injured to walk, from the human food supply.

Senator Byron Dorgan, a North Dakota Democrat, urged the administration to back an amendment approved by the Senate last month — but dropped in the final bill by the House of Representatives — that would prohibit US slaughter plants from using downer cattle in beef for human consumption.

In Washington state today, a state dairy group said the US Department of Agriculture (USDA) could order the slaughter of the cattle herd that included the cow with the disease if officials found other cows were infected.

“It may not be a situation where the entire herd is taken, but it is a possibility,” said Steve Matzen, general manager of the Washington State Dairy Council.

“But we’ll probably rely on the USDA as they make those calls based on science.”

A Democratic presidential hopeful, Ohio Representative Dennis Kucinich, said he would introduce legislation next month to ban downer cattle from the human food supply.

Presidential candidate Howard Dean has also criticised Republicans for killing the Senate proposal to ban US meatpackers from using downer cattle in the human food supply.

Mad cow, or bovine spongiform encephalopathy (BSE), is a fatal disease that destroys the brains of infected cattle. Humans can contract a form of the disease known as variant Creutzfeldt-Jakob Disease by eating tissue from the brains, spinal cords or central nervous systems of infected animals.

At least 137 people died from the human variant after mad cow disease struck herds in Britain and Europe a decade ago.

US officials have repeatedly said there is no risk to consumers from the recall of 10,000 pounds of beef linked to the infected cow and 19 others slaughtered on December 9.

Consumer groups have said the Bush administration was considering several possible regulatory changes to boost consumer confidence, in addition to increased testing.

In addition to the political fallout, White House officials struggled with the economic impact of the disease just as the US economy was showing signs of strength.

USDA officials reported more evidence yesterday the infected Holstein cow in Washington state was born in Canada in April 1997, a link the USDA hopes will reassure US trade partners.

But the growing evidence of a Canadian link failed to persuade Japan to reconsider its ban on importing US beef.