ver since he identified the bizarre brain-destroying proteins that cause mad cow disease, Dr. Stanley Prusiner, a neurologist at the University of California at San Francisco, has worried about whether the meat supply in America is safe.
He spoke over the years of the need to increase testing and safety measures. Then in May, a case of mad cow disease appeared in Canada, and he quickly sought a meeting with Ann M. Veneman, the secretary of agriculture. He was rebuffed, he said in an interview yesterday, until he ran into Karl Rove, senior adviser to President Bush.
So six weeks ago, Dr. Prusiner, who won the 1997 Nobel Prize in Medicine for his work on prions, entered Ms. Veneman's office with a message. "I went to tell her that what happened in Canada was going to happen in the United States," Dr. Prusiner said. "I told her it was just a matter of time."
The department had been willfully blind to the threat, he said. The only reason mad cow disease had not been found here, he said, is that the department's animal inspection agency was testing too few animals. Once more cows are tested, he added, "we'll be able to understand the magnitude of our problem."
This nation should immediately start testing every cow that shows signs of illness and eventually every single cow upon slaughter, he said he told Ms. Veneman. Japan has such a program and is finding the disease in young asymptomatic animals.
Fast, accurate and inexpensive tests are available, Dr. Prusiner said, including one that he has patented through his university.
Ms. Veneman's response (he said she did not share his sense of urgency) left him frustrated. That frustration soared this week after a cow in Washington State was tentatively found to have the disease. If the nation had increased testing and inspections, meat from that cow might never have entered the food chain, he said.
Ms. Veneman was not available for interviews yesterday, and the White House referred all questions to the department. A spokeswoman for Ms. Veneman, Julie Quick, said: "We have met with many experts in this area, including Dr. Prusiner. We welcome as much scientific input and insight as we can get on this very important issue. We want to make sure that our actions are based on the best available science."
In Dr. Prusiner's view, Ms. Veneman is getting poor scientific advice. "U.S.D.A. scientists and veterinarians, who grew up learning about viruses, have difficulty comprehending the novel concepts of prion biology," he said. "They treat the disease as if it were an infection that you can contain by quarantining animals on farms. It's as though my work of the last 20 years did not exist."
Scientists have long been fascinated by a group of diseases, called spongiform encephalopathies, that eat away at the brain, causing madness and death. The leading theory was that they were caused by a slow-acting virus. But in 1988, Dr. Prusiner proposed a theory that seemed heretical at the time: the infectious agent was simply a type of protein, which he called prions.
Prions (pronounced PREE-ons), he and others went on to establish, are proteins that as a matter of course can misfold — that is, fold themselves into alternative shapes that have lethal properties — and cause a runaway reaction in nervous tissue. As more misfolded proteins accumulate, they kill nerve cells.
Animals that eat infected tissues can contract the disease, setting off an epidemic as animals eat each other via rendered meats. But misfolded proteins can also arise spontaneously in cattle and other animals, Dr. Prusiner said. It is not known whether meat from animals with that form of the disease could pass the disease to humans, he said, but it is a risk that greatly worries him.
Cattle with sporadic disease are probably entering the food chain in the United States in small numbers, Dr. Prusiner and other experts say.
Brain tissue from the newly discovered dairy cow in Washington is now being tested in Britain to see if it matches prion strains that caused the mad cow epidemic there, or if it is a homegrown American sporadic strain, Dr. Prusiner said.
"The problem is we just don't know the size of the problem," he said. "We don't know the prevalence or incidence of the disease."
The Japanese experience is instructive, Dr. Prusiner said. Three and a half years ago, that country identified its first case of mad cow disease. The government then said it would begin testing all cows older than 30 months, as they do in Europe. Older animals presumably have a greater chance of showing the disease, Dr. Prusiner said.
Japanese consumer groups protested and the government then said it would test every cow upon slaughter, Dr. Prusiner said. The Japanese have 4 million cattle and slaughter 1.2 million of them each year. The United States has 100 million cattle and kills 35 million a year.
Early this fall, Japanese surveillance found two new cases of the disease in young animals, aged 21 and 23 months. "Under no testing regime except Japan would these cases ever be found," he said.
The 23-month-old cow tested borderline positive using two traditional tests. But the surveillance team then looked in a different part of the brain using an advanced research technique and found a huge signal for infectious material, Dr. Prusiner said. It was a different strain of the disease, possibly a sporadic case.
The only way to learn what the United States is facing is to test every animal, Dr. Prusiner said. Existing methods, used widely in Europe and Japan, grind up brain stem tissue and use an enzyme to measure amounts of infectious prions. Animals must have lots of bad prions to get a clear diagnosis.
Newer tests, by a variety of companies, are more sensitive, cheaper and faster. Dr. Prusiner said that his test could even detect extremely small amounts of infectious prion in very young animals with no symptoms. Sold by InPro Biotechnology in South San Francisco, a single testing operation could process 8,000 samples in 24 hours, he said.
British health officials will start using the test in February, Dr. Prusiner said. If adopted in this country, it would raise the price of a pound of meat by two to three cents, he said.
"We want to keep prions out of the mouths of humans," Dr. Prusiner said. "We don't know what they might be doing to us."
His laboratory is working on promising treatments for the human form of mad cow disease but preventing its spread is just as important, he said. "Science is capable of finding out how serious the problem is," he said, "but only government can mandate the solutions."