Q & A: Some facts on 'mad-cow' disease

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The discovery today of a Mabton, Washington cow infected with "mad-cow" disease, or bovine spongiform encephalopathy (BSE), has consumers asking where our beef comes from, how cattle get the disease and how people can get it from cows.

Though the human form of BSE is frightening, most experts say Americans' risk of contracting the disease is extremely low.

This is the first case of BSE detected among cattle in this country.

The questions are many. Here are some answers:

Q. Does the United States import beef from countries where "mad-cow" disease is considered a risk?

A. No. After the Canadian case was discovered, the United States banned imports of Canadian beef or cattle. Since 1997, both countries have prohibited such imports from Europe, where a "mad-cow" outbreak occurred in the 1990s and where some cases still occur. More than 95 percent of cases detected worldwide have been in the United Kingdom. No known cases have occurred in the United States.

Q. Can authorities trace every steak, roast or package of hamburger in the supermarket to its precise origin?

A. No. However, all can be traced at least to a particular packing plant, and in some cases to a certain feedlot or farm, Wahl said. A batch of ground beef, which may mix meat from many cows, may be traceable only to a group of farms rather than a single farm.

Q. Which parts from an infected animal would most likely harbor the disease?

A. The brain and spinal cord, since BSE appears to affect primarily neurological tissue. A steak would be far less likely to carry the disease, said Donald Knowles, a researcher in animal-infectious diseases at WSU. Processed products such as sausage could contain brain tissue but not necessarily.

Q. Will cooking or freezing infected meat destroy the disease?

A. No.

Q. How is "mad-cow" disease spread among cattle?

A. Most likely through feed that contains rendered parts of BSE-infected cattle, experts say. The United States and Canada have both banned giving feed containing rendered cattle parts to other cows. Studies indicate the disease is not spread from one live cow to another, nor from a mother cow to its calf.

Q. How is BSE confirmed in cows?

A. A cow must be destroyed and its brain examined. Brains of infected cows take on an abnormal, sponge-like formation. However, researchers are working to develop a blood test that can be performed on live cows.

Q. How much BSE testing is being done in the United States?

A. About 19,000 tests a year, according to the USDA.

Q. Is that enough?

A. The issue is debated. Critics contend it's too few, given a national herd of some 100 million. Jan Busboom, an animal-sciences professor at WSU, believes it's sufficient. The tests, performed largely on older or ailing animals, help rule out the risk of meat from any BSE-infected cows entering the food chain, he said. Tests also are performed on randomly selected younger cows.

Q. How do people contract "mad-cow" disease?

A. Scientists think the disease can be transmitted through contaminated beef, especially parts of the central-nervous system such as the brain. They think it is caused by an abnormal prion, a cellular protein, which folds incorrectly in the cells. There is no evidence of transmission through person-to-person contact. Some animal studies suggest the protein could be transmitted by blood, but this has never been shown in humans, according to the National Institute of Neurological Disorders and Stroke. No known cases of the disease, in cows or humans, have occurred in the United States.

Q. What does this abnormal protein do to you?

A. It causes the brain to become filled with holes that resemble sponges under a microscope. The disease is one of several called spongiform encephalopathy. Early symptoms include psychiatric or sensory problems. Muscle coordination deteriorates in weeks to months, and muscle jerking and severe dementia occur late in the illness. Death may take several years, but the disease is invariably fatal.

Q. Isn't there a naturally occurring form of the disease?

A. Yes. It's called Creutzfeldt-Jakob Disease, or CJD. About 85 percent of all forms of this classic CJD occur sporadically, with no known risk factor. Another 5 to 10 percent are inherited. About 200 cases of CJD are reported in the United States each year.

Q. What is the difference between classic CJD and "mad-cow" disease?

A. A person with classic CJD usually starts having symptoms in his or her 60s. Unlike the early psychiatric symptoms of "mad-cow" disease, classic CJD symptoms begin with poor muscle coordination, personality changes and impaired memory, thinking and vision. Mental impairment soon becomes severe, and the patient may have muscle jerking and go blind. Death usually occurs within a year.

In contrast, symptoms of "mad-cow" disease - also known as new variant CJD - typically begin at a much younger age (of the more than 120 deaths in the United Kingdom, more than half have been in people under 30), and the symptoms may last for years before death.

Scientists believe symptoms begin many years - perhaps 10 or more - after a tainted product was eaten.

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