Mad cow case found, but meat supply deemed safe

U.S. officials announced a case of mad cow disease in a dairy cow in California. It is only the fourth such case detected in the U.S. since the first case was identified in 2003.

Q: Is it safe to drink milk or eat beef?

A: Yes. The new case is a dairy cow, and officials say the disease can't be transmitted in milk.

Q: What is mad cow disease?

A: Mad cow disease is the common term for bovine spongiform encephalopathy, or BSE. It's a degenerative nerve disease in cattle that kills brain cells and leaves spongy holes in the brain.

Q: How do cows get mad cow disease?

A: BSE is believed to be caused by disease-carrying proteins called prions, not viruses or bacteria. Animals can become infected when they eat BSE-tainted tissue. But scientists say the newly diagnosed California cow got the disease from a random genetic mutation, not from eating infected cattle feed.

Q: Can humans get mad cow disease?

A: Yes. BSE is linked to a rare but fatal human brain disease, variant Creutzfeldt-Jakob disease. People get it by eating beef products contaminated with mad cow disease. Only three cases have been confirmed in the United States, but health officials say those were linked to meat products in the United Kingdom and Saudi Arabia.

Q: How was the latest case spotted?

A: The case was discovered through routine testing of a cow that was being sent to a rendering plant in central California. Rendering plants process dead animals and animal waste for use in such things as animal feed and industrial fats and oils. Testing involves taking samples from the brains of dead animals from farms, slaughterhouses and livestock markets.