You might have heard news reports about mad cow disease and wondered: What the heck is that? Mad cow disease is an illness also known as bovine spongiform encephalopathy (say: 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. An infected cow would act "mad," which sometimes means mentally ill.

A cow with BSE develops these problems because it has developed an infection. This infection causes its brain to waste away and become spongy. Researchers are not completely sure how cows get this kind of infection, but they believe it comes from certain kinds of food given to cows. Some of this food contains the remains of dead cows that had the infection. These remains, especially the brains and spinal cords, may contain BSE.

Because BSE was a problem in the United Kingdom, the United States enacted rules to prevent live cows and some cow products from entering this country. The United States has had two cases of BSE in cows — one in 2003 and one in 2005. In both cases, the government took steps so that people wouldn't buy and eat the meat.

What Does This Have to Do With People?

BSE is a concern because it can be transmitted to people if they eat meat that came from a cow with BSE. If a person eats BSE-infected beef, the person is at a higher risk for getting a human form of the disease, called Creutzfeldt-Jakob disease, or CJD. It is a very serious disease that affects the brain, but CJD is very rare in the United States. Only 1 in a million people get it. And it is not contagious, meaning a person can't catch it from someone who has it. Likewise, a cow that has BSE can't infect other cows.

The discovery of the BSE cases in the United States increases concern about the human form of the disease, but it's still very unlikely that you or anyone you know will get the disease.

What's Being Done About BSE?

Many people in the United States are working to prevent BSE-contaminated beef from getting to stores. There are rules against beef processors using the brains or spinal cords of the animal to make food products. In addition, there is a testing system in place designed to identify cows that may have the disease. There's also a recall system that allows companies to notify consumers and pull products off store shelves if there could be a problem with them.

What Should I Do?

If you're worried about mad cow disease, tell the person who buys the food in your household about how you feel. Some cuts of meat carry less risk of transmitting the disease than ground beef, which is used to make hamburgers.

Being a kid, you might be wondering about milk. Even though it comes from cows, BSE cannot be transmitted through milk or milk products.

Reviewed by: Steven Dowshen, MD
Date reviewed: January 2013