February 10, 2004 Sacramento Bee by JON ORTIZ

That's the one thing that U.S. agriculture officials, foreign governments and consumer groups can agree on.

Looking at how the United States tests for mad cow disease illuminates why estimates on the number of other infected cows range from zero to the thousands. And it also shows why opinions vary on how best to test for bovine spongiform encephalopathy, or mad cow disease.

The U.S. Department of Agriculture will not guess the number of undetected mad cows, saying its testing is not a scientific sampling that allows extrapolation, nor is it designed to keep the food supply safe.

"We cannot give you a specific count (of potentially diseased animals) because that's not what our surveillance program is designed to do," said Jim Rodgers, spokesman for the USDA's Animal and Plant Health Inspection Service, which oversees mad cow testing.

"The program isn't designed to find every case of disease," he said. "It's not designed so that a rancher can say, 'I raise only 100 percent (mad cow)-free beef.' "

Although the inspection service tested the brains of 20,000 of the 35 million cows slaughtered in the United States last year, most of those were so-called "downers" too sick to walk. Those were targeted because scientists think such animals are at highest risk for mad cow. Cows in the throes of the disease often can't walk, and downer cows usually are older than 30 months - the generally accepted incubation time for mad cow.

Of the cattle slaughtered in the United States last year, approximately 200,000 were downers.

By narrowing its focus to high-risk animals, the USDA says that its mad cow surveillance can catch one mad cow in a cattle population of 1 million. By that notion, 35 of the 35 million cows slaughtered in the U.S. last year could have been infected and their meat sold in stores and restaurants like the infected cow found in Mabton, Wash.

But the USDA's narrow sampling pool makes that math impossible. Its program does not use scientific sampling by which a random sample statistically represents a larger population.

The USDA, which plans to test 38,000 cows this year, estimates it would need to test 3 million cows chosen by scientific sampling to accurately reflect the overall health of the 100 million cows in the U.S. herd.

But the department stands by its mad cow program, saying it tests cows most likely to be sick. "Our program is supposed to determine if there is a disease in a population of animals, that's it," Rodgers said.

The USDA banned "downer" cows from the food supply on Dec. 30. It has not set new standards for how many downer cows and how many apparently healthy cows will be tested.

Praise for the testing program has come from the very top of the USDA, with Agriculture Department Secretary Ann Veneman characterizing it as "aggressive."

Consumer groups, however, have criticized the process for years.

"This is an agency that has created and maintained an unscientific test program that doesn't address public health issues," said Felicia Nestor of the Government Accountability Project.

Harvard risk analyst Joshua Cohen said that the number of BSE-infected cattle in the national herd could range between "zero and a few thousand." The reason for the wide swing, he said, is that the USDA targeted downer cows, skewing the math.

"Those factors taken together mean that (the Washington cow) could be an unusual case," Cohen said. "This wasn't a random sample. It was a sample targeted at a particular kind of cow. That means you can't project with any certainty how many other cows in the general population are sick."

Cohen co-authored a 2001 study on mad cow disease by Harvard's Center for Risk Analysis. The USDA often cites the study as proof their system is adequate.

"I believe we're in the lower end of that range, but I wouldn't bet my life that no more cases exist," Cohen said. "You can never say never."

He thinks that limited testing is acceptable, given its cost and relatively low risk of human illness - as long as testing targets high-risk cows.

"When you're looking for a needle in a haystack, you've got to look through a lot of hay," he said. "Unless the needle has shaken down to the bottom so you can narrow down where to look for it."

USDA critics say the current system is full of holes that put public health at risk.

In the 12 years from 1990 to 2001, 16,829 cattle in the United States were tested for mad cow. Then the Harvard study called for more testing, and the USDA upped the number to 19,990 in 2002 and 20,543 last year.

"This country isn't serious about finding the disease now, and we were positively sleepwalking a few years ago," said Ira Krull, a mad cow expert at Northeastern University and outspoken critic of the USDA.

Nestor and other consumer advocates, including Consumers Union and the Consumer Federation of America, want the USDA to adopt the United Kingdom's mad cow policy. The UK tests every cow older than 30 months - a program that caught 425 cases there last year.

Adopting the same policy here would mean testing more than 6.3 million cow brains annually, or about 17,000 brains per day at a cost of about $50 each.

The beef industry hates the idea of casting the mad cow net wider, saying more tests are needless and costly and that fears about infected cows in the food chain are unfounded.

"It would be like a physician testing every patient who walked in the door - male, female, young or old - for prostate cancer," said Ben Higgins, spokesman for the California Cattlemen's Association, which supported the USDA's ban on downer cows from human consumption. "We feel that the current safeguards against the introduction and spread of BSE in the U.S. are highly effective."