Mad cow disease seems to pop up in the news now and then. But what is it, and how likely are people to get it?

What Is Mad Cow Disease?

Mad cow disease is an incurable, fatal brain disease that affects cattle and possibly some other animals, such as goats and sheep. The medical name for mad cow disease is bovine spongiform encephalopathy (pronounced: bo-vine spun-jih-form en-seh-fah-la-puh-thee), or BSE for short. It's called mad cow disease because it affects a cow's nervous system, causing a cow to act strangely and lose control of its ability to do normal things, such as walk.

How Do People Get It?

Only certain animals can get BSE — people don't actually get mad cow disease. However, experts have found a link between BSE and a rare brain condition that affects people, called variant Creutzfeldt-Jakob disease (vCJD). Researchers believe that people who eat beef from cows that have BSE are at risk of developing a form of vCJD.

vCJD is caused by an abnormal type of protein in the brain called a prion. When people have vCJD, cells in the brain die until the brain eventually has a "sponge-like" appearance. During this time, people with the disease gradually lose control of their mental and physical capabilities.

To date, very few people have been diagnosed with vCJD. By October 2009, only 217 cases of this rare condition had been reported worldwide. Of these, most were identified in Britain. Several of the people diagnosed with the disease outside Britain — including two cases in the United States — had a history of exposure in Britain. Experts believe that the people got vCJD after eating beef products from cows that had BSE.

Because vCJD is relatively new and extremely rare, experts are still learning about it. However, researchers believe that the disease is not contagious among people. In other words, you cannot get vCJD from someone else who has it. At present, it appears that the main way people get the disease is from eating contaminated meat.

Experts don't yet know exactly how long the incubation period is for vCJD (in other words, how long it takes from the time a person contracts it to the time that symptoms first appear). However, they do believe that it takes years, if not decades, from the time someone is exposed to the disease until the first signs appear. After the first signs appear, the brain can deteriorate within a year. At this time, there is no known treatment for the disease.

What's Being Done?

If you're worried about mad cow disease, tell whoever buys the food in your household about how you feel. The type of protein that causes mad cow disease cannot be removed or destroyed when beef is processed or cooked. For this reason, the U.S. government has established several meat processing procedures to protect the public. One of these steps involves removing the parts of the cow that are at highest risk of containing BSE-causing proteins — the brain and spinal cord — to reduce the chances of them contaminating the meat people eat.

In 2009, the U.S. Food and Drug Administration (FDA) put into place additional safeguards to help protect consumers from BSE. These prohibit the use of any high-risk cattle materials in the feed of any animal. In this way, the FDA continues to decrease the already tiny possibility of infection with BSE.

There is also a system in place to test samples of animals regularly. The testing system helped officials identify some contaminated meat in Washington state in December 2003 — one of only three cases of mad cow disease found in the United States so far.

The government has a recall policy for meat that's suspected of being contaminated.

If you're wondering if you can get sick from drinking cow's milk, the FDA says there is no evidence that the disease is transmitted through cow's milk and milk products.

The good news is that it's highly unlikely that a person will contract vCJD from eating beef. vCJD itself is very rare. And because of the control measures now in place, the chance that you will eat meat infected with BSE is extremely low.

Reviewed by: Larissa Hirsch, MD
Date reviewed: May 2010