The US government is investigating a possible new case of mad cow disease, officials said on Thursday, rattling the US cattle industry, food processors and beef-oriented restaurant chains.
Additional checks are being conducted after initial testing proved inconclusive on the suspect brain tissue. Officials said the suspect animal never entered the food or feed chain.
Ranches and businesses dependent on beef are still feeling financial effects from the only confirmed US case.
More than 40 countries cut off imports of US beef after a Canadian-born Holstein was found to have been infected in Washington state last December.
Many of those bans remain in place. The announcement of a possible new case comes less than a month after US negotiators reached tentative agreements with both Japan and Taiwan to resume US beef and beef product shipments.
Exports represent about US$3.8 billion of America's US$40 billion a year beef industry.
Thursday's announcement sent cattle prices tumbling on fears that foreign markets would remain closed to US beef. Shares of McDonald's, Wendy's, and other restaurant chains that feature hamburgers also slumped, as did those of US meat producers.
The US Department of Agriculture (USDA) gave no information on the location or origin of the slaughtered animal and said results from advanced tests were not expected before four to seven days.
Alisa Harrison, a USDA spokeswoman, said the animal in question was among high-risk animals subjected to the new screening procedures. Those are animals that died on the farm, have trouble walking or showed signs of nerve damage.
She said no quarantines have been established.
"There's no reason to do that since it's an inconclusive result," Harrison said. "Should it be positive, we will be ready."
The "inconclusive result" was the same term the agency used in June when two potential cases turned out to be false alarms.
The Consumer Federation of America suggested that the "inconclusive" label was itself misleading, and that the government should have reported the finding as a "preliminary positive." Still, said federation official Carol Tucker, "there is no reason for consumers to be alarmed by the announcement."