The federal government insists that American beef is safe, but doubts linger among importing nations.
The new case of mad cow disease in the United States points to the US Department of Agriculture's two basic and - critics say - potentially conflicting mandates.
The agency is charged with ensuring the safety of US agricultural products. But it's also meant to promote those products domestically and abroad. Bad news in the first area can harm the second.
Seeking to lessen any concern beef-eaters may have about the recently discovered cow infected with the disease, Agriculture Secretary Mike Johanns speaks of "interlocking safeguards" and "the firewalls we have in place." He points to the vastly increased number of cows that now are screened for the deadly infection - more than 388,000 in the past 18 months. Before the first US case of mad cow disease was discovered in December 2003, just a few thousand cows were tested annually.
But the388,000 are still less than 2 percent of the approximately 35 million cattle slaughtered in the US each year, far lower than the percentage tested in Europe or Japan. And the most recent episode also shows how that system of checking - even with its improvements - is not foolproof.
Mad cow is known scientifically as "bovine spongiform encephalopathy" (BSE). It's a brain-wasting disease believed to be carried by animal feed made from cattle brains or spinal cord. Such feed is now banned in the US and other countries, but that hasn't stopped BSE from appearing around the world.
The first test on the suspected cow showed positive signs of BSE. A second, more detailed test showed no signs of the disease. But the department's inspector general ordered a third round of more rigorous testing at a lab in England, and that confirmed that the animal indeed had been infected with mad cow disease.
For producers and USDA officials, just one case out of 388,000 indicates the relative safety of the system.
The bottom line, says Terry Stokes, CEO of the National Cattlemen's Beef Association, is that "the animal did not enter the human food or animal feed supply."
Most beef-eating Americans apparently have not changed their habits as a result of the mad cow episodes. But the industry, the largest segment of US agriculture, knows that its foreign market remains a large problem.
"US beef is safe," says Mr. Stokes, "and we urge USDA to do everything within its power to send that message to our trading partners."