What is mad cow disease?

Variant Creutzfeldt-Jakob disease (vCJD) causes the brain to become damaged over time. It is fatal. Symptoms include:

• Tingling, burning, or prickling in the face, hands, feet, and legs. But there are much more common illnesses that cause these same symptoms. Having tingling in parts of your body does not mean you have vCJD.
• Dementia.
• Psychosis.
• Problems moving parts of the body. As the disease gets worse, a person is no longer able to walk.
• Coma.

If a person does eat nerve tissue from an infected cow, he or she may not feel sick right away. The time it takes for symptoms to occur after you're exposed to the disease is not known for sure, but experts think it is years.

There is no cure for variant Creutzfeldt-Jakob disease (vCJD). Treatment includes managing the symptoms that occur as the disease gets worse.

The following health organizations are tracking and studying mad cow disease and variant Creutzfeldt-Jakob disease (vCJD). Their websites contain the most up-to-date information about these diseases.

• U.S. Centers for Disease Control and Prevention (CDC) provides up-to-date information about mad cow disease and variant Creutzfeldt-Jakob disease (vCJD), including tracking, prevention, travel precautions, and food inspection. You can find information at www.cdc.gov/prions/bse/index.html.
• U.S. Department of Agriculture (USDA) provides information about mad cow disease, the safety of the meat supply in the United States, and infection control guidelines. You can find information at www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/production-and-inspection/bovine-spongiform-encephalopathy-mad-cow-disease/bse-mad-cow-disease.
• Health Canada answers frequently asked questions about mad cow disease and vCJD and provides information about infection control and food inspection. You can find information at www.phac-aspc.gc.ca/cjd-mcj/index-eng.php.
• The World Health Organization (WHO) website offers information about mad cow disease and vCJD cases around the world and provides infection control guidelines. You can find information at www.who.int/csr/disease/bse/en.

There is no single test to diagnose variant Creutzfeldt-Jakob disease (vCJD). Doctors may think that a person has vCJD based on where the person has lived and the person's symptoms and past health. Imaging tests, such as an MRI, may be done to check for brain changes caused by vCJD. Other tests may include a lumbar puncture or an electroencephalogram (EEG).

A brain biopsy is the only way to confirm a diagnosis of vCJD.

When a cow is slaughtered, parts of it are used for human food and other parts are used in animal feed. If an infected cow is slaughtered and its nerve tissue is used in cattle feed, other cows can become infected.

People can get variant Creutzfeldt-Jakob disease (vCJD) if they eat the brain or spinal cord tissue of infected cattle.

There is no evidence that people can get mad cow disease or vCJD from eating muscle meat—which is used for ground beef, roasts, and steaks—or from consuming milk or milk products.

People with vCJD cannot spread it to others through casual contact.

Experts are not sure what causes mad cow disease or variant Creutzfeldt-Jakob disease (vCJD).

The leading theory is that the disease is caused by infectious proteins called prions (say "PREE-ons"). In affected cows, these proteins are found in the brain, spinal cord, and small intestine. There is no proof that prions are found in muscle meat (such as steak) or in milk.

Mad cow disease is a fatal disease that slowly destroys the brain and spinal cord (central nervous system) in cattle. It also is known as bovine spongiform encephalopathy, or BSE.

People cannot get mad cow disease. But in rare cases they may get a human form of mad cow disease called variant Creutzfeldt-Jakob disease (vCJD), which is fatal. Over time, vCJD destroys the brain and spinal cord.