It's too soon to shun steaks, experts say

Disease specialists see danger as minimal, say they'll eat beef as usual

December 25, 2003|By Jonathan Bor | Jonathan Bor,SUN STAFF

Their advice might not seem entirely satisfying, but experts in mad cow disease say consumers should feel safe chowing down on American beef as long as the disease is not found in additional U.S. cows.

The single case of mad cow disease discovered in Washington state this week poses a vanishingly small - perhaps nonexistent - risk, they say, unless evidence of a wider epidemic turns up later.

"I had beef for dinner last night after I heard the news reports," said Dr. Richard T. Johnson, a neurologist and expert on brain-wasting diseases at the Johns Hopkins School of Medicine.

"I felt that was less risky than driving the car into work this morning, which I'm sure it is. The risk is extraordinarily low, though I can't say it's zero."

Dr. J. Glenn Morris Jr., chairman of the epidemiology department at the University of Maryland School of Medicine and a specialist in a food safety, said there is no threat to the nation's food supply.

"I would not change my buying habits or do anything different," said Morris, who has advised the federal government on food safety. "The USDA [Department of Agriculture] has been regularly screening cattle, and up to now they have found nothing. It's highly likely this is an isolated event."

Fresh in everyone's mind, however, is the United Kingdom's experience with mad cow disease in the 1990s. There, it infected 60,000 to 80,000 cattle and devastated the country's beef industry. About 150 people have become ill there, presumably after eating infected meat.

In humans, the illness is called variant Creutzfeldt-Jakob disease - similar to a disease that appears only in humans but, like mad cow, causes the brain to become spongy and riddled with holes. Both cause muscle twitching and various psychiatric symptoms before ultimately proving fatal within three to 12 months.

Both mad cow and Creutzfeldt-Jakob disease belong to a family called spongiform encephalopathies, caused by mutant proteins called prions. Although their function is unknown, normal prion proteins are present in everyone - but a mutation can cause them to fold abnormally and destroy nerve tissue.

Human Creutzfeldt-Jakob is caused by a spontaneous mutation during a person's lifetime and is not spread to others, although similar illnesses have been transmitted by cannibalism in remote societies. It is exceedingly rare, occurring about once in every 1 million people.

Although mad cow disease is usually spread among cattle through feed that contains infected cattle brains and spinal cords, some scientists believe a single case can also arise from spontaneous mutation. That's a good scenario, unless pieces of that cow's nervous system enter the cattle feed supply.

"If this is one spontaneous case, then this is not the tip of the iceberg," Johnson said of the Washington discovery. "That would be it, a flash in the pan."

Although cattle naturally eat grain and grass, ranchers and feed lot operators at one time gave them feed with protein from otherwise wasted parts of slaughtered cows - including brains and spinal cords - that can carry mad cow disease.

To prevent the spread of the disease, the federal government now bans the use of brain or spinal cord material in cattle feed. It also prohibits feeding the body parts of ruminants - sheep, goats and cattle - to other ruminants.

"The cattle rendered can be fed to chickens or pigs, but not back to cows or sheep or goats," said Johnson.

Enforcing the ban, however, is extremely difficult. Small feed manufacturers might process different types of feed in the same facility, creating the possibility of cross-contamination of equipment and bags.

Also, he said, farmers might privately decide to use feed meant for one type of animal on another because it's cheaper or more readily available.

"The reality is that it's not tightly policed," said Morris. "There has been a lot of concern on the part of the public health community that there are many holes in the system."

Morris said a major failure in the feed ban could cause a significant outbreak among humans. Britain's problem was caused by the recycling of ruminant parts into ruminant feed.

The government's investigation, which involves testing cattle from the herd where the sick cow from Washington state was born, should determine whether the disease is confined to one animal.

If that's the case, consumers can rest assured that the chance of getting sick from any beef product is virtually nonexistent, experts say. Although it might not be of much comfort, they note that the British cattle epidemic caused only a limited outbreak among humans.

At first, scientists thought the human cases in Britain were the leading edge of a looming nightmare, under the theory that a person harboring the prions might not become sick for decades. Instead, Morris said, new cases have tapered off considerably, leading many to conclude that the average incubation period could be much shorter.

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