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."
That has been an uphill battle. Over the weekend, Taiwan reimposed a ban on imports of American beef. Japan, which had been the largest importer of US beef, has yet to lift the ban it imposed after the 2003 discovery.
In the wake of the first US case of mad cow, the USDA imposed new rules. "Downer" cattle - those injured or too sick to stand - may not be used for human food, and slaughterhouses may not use techniques that can mix brain or spinal-cord tissue with muscle meat.
Consumer groups say the government must take additional steps, including more testing, tighter controls, and the closer tracking of beef cows and their offspring as they're brought and sold.
The latest episode "underscores the need for federal regulations on BSE to be tightened immediately," says Wenonah Hauter, who heads Public Citizen's food program.
Ms. Hauter says federal agencies "must eliminate loopholes in the current feed ban which still allow the use of cattle blood, waste from the floors of poultry houses, and processed restaurant and food waste to be fed to cattle."
"The use of rendered cattle remains is allowed in feed for hogs and poultry, and in turn, hog and poultry remains can be put back into cattle feed," she says. "All of these loopholes provide pathways for cattle to eat potentially infective tissue from other cattle and create the potential for the disease to spread."
Although about 150 people in Europe died of the human form of the disease in the 1980s and 1990s, no such cases have been reported in the US.
To increase the level of safety, Agriculture Secretary Johanns has ordered his department to undertake two additional tests for BSE if the first test is inconclusive.
"I want to make sure we continue to give consumers every reason to be confident in the health of our cattle herd," says Johanns.
"The risk of contracting the human form of mad cow disease is minuscule," agrees Caroline Smith DeWaal, food safety director at the Center for Science in the Public Interest.
"But since the United States does not have a mandatory animal tracking system," she adds, "USDA strategy is basically to cross its fingers and hope that beef from a BSE-infected animal doesn't end up on Americans' dinner plates."