This can happen if you eat nerve tissue (the brain and spinal cord) of cattle that were infected with mad cow disease. Over time, vCJD destroys the brain and spinal cord.
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.
People who have spent a lot of time (at least 3 months) in places where mad cow disease has been found are not allowed to give blood in the United States or Canada.2, 1 This is to help prevent vCJD from spreading.
What causes mad cow disease and variant Creutzfeldt-Jakob disease (vCJD)?
Experts are not sure what causes mad cow disease or 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.
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 vCJD if they eat the brain or spinal cord tissue of infected cattle.
How common are mad cow disease and vCJD?
The first case of vCJD was reported in 1996. Since then, there have been a few cases of vCJD reported in the world. Most of the cases have been in countries that are part of the United Kingdom (England, Scotland, Wales, and Northern Ireland).
In December 2003, mad cow disease was discovered in one cow in the United States. Before this cow was found to have the disease, the cow was slaughtered and its muscle meat was sent to be sold in grocery stores. But its organs and nerve tissue were not used for human food. Although mad cow disease cannot be spread through muscle meat, the United States Department of Agriculture (USDA) quickly traced the meat and removed it from grocery stores.
Since 2004, only three more cows in the United States have been found to have mad cow disease. The most recent case of BSE was found in April 2012 in a cow in California.