Mad Cow Disease and vCJD: Should I Worry?

Medically Reviewed by Jabeen Begum, MD on February 06, 2024
7 min read

Mad cow disease, or bovine spongiform encephalopathy (BSE), is a neurological disease in cattle that gets worse over time. Instead of viruses or bacteria, it's caused by an infection from an abnormal version of a protein, called a prion. For reasons still unknown, this protein becomes harmful and destroys nervous system tissue in the brain and spinal cord.

Scientists think the first cases of BSE happened in the U.K. in the 1970s. Two cases were found in 1986. It's possible the disease arose first when cattle were fed meat-and-bone meal containing the BSE prion. It also may have come from products from sheep with a prion disease called scrapie. The outbreak spread in the U.K. because young calves were eating prion-infected meat-and-bone meal. Cows don't get BSE from being near other cows that have it. But it can be transmitted through the food supply.

An outbreak of mad cow disease peaked in the U.K. in 1993, with about 1,000 cases every week. By the end of 2015, the U.K. had recorded more than 184,500 cases. But BSE is a lot less prevalent now, with only two cases reported in the U.K. in 2015.

The U.S. Department of Agriculture (USDA) has tested hundreds of thousands of cattle for BSE. But as of August 2018, only 6 cases have ever turned up in the U.S. and another 20 cases in Canada. The levels of BSE in the U.S. and Canada are so low it's hard to measure it. The best estimates suggest there are 0.167 cases per million in the U.S. and three to eight cases per million in Canada.

What does mad cow disease look like in cattle?

A cow with BSE may have trouble walking or standing up. They may seem nervous or aggressive. But it usually takes 4-6 years after a cow is infected with prions for it to show any signs of illness. There's no test for BSE in a living cow either. Once symptoms show up, cows usually die within weeks or months.

When people get this disease, it isn't called mad cow. The human version of BSE is called variant Creutzfeldt-Jakob disease (vCJD). There's strong evidence people can get vCJD by eating beef products with central nervous system tissue, such as brain and spinal cord, from cattle infected with mad cow disease.

According to the CDC, four cases of vCJD have been reported in the U.S. But all of the people who developed vCJD in the U.S. had lived in other parts of the world, including the U.K. and Saudi Arabia. There's no record of anyone getting vCJD from eating infected beef in the U.S.

It's important to understand the differences between variant CJD and another form of CJD, called classic or sporadic CJD. Classic CJD has no known cause and occurs each year at a rate of one to two cases per million people throughout the world, including the U.S. and countries where mad cow disease has never been reported. It's not linked to eating mad cow disease-affected cattle; both vegetarians and meat eaters have died from classic CJD. CJD most commonly affects people over 65 and is usually fatal within 6 months of the onset of symptoms.

The disease can affect all age groups and is very hard to diagnose until it has nearly run its course. In the early stages of vCJD, people have symptoms related to the nervous system, such as depression and loss of coordination. Later in the illness, dementia develops. But only in advanced stages of the disease can brain abnormalities be detected by an MRI. vCJD is fatal, usually within 13 months of the onset of symptoms.

Early symptoms of vCJD include:

  • Severe depression
  • Withdrawing from family and friends
  • Anxiety
  • Irritability
  • Trouble sleeping (insomnia)

Advanced symptoms of vCJD include:

  • Loss of coordination, causing trouble with walking, speaking, and balance
  • Muscle twitches or spasms
  • Incontinence
  • Loss of bowel control
  • Vision loss or blindness
  • Loss of movement
  • Memory loss
  • Trouble concentrating
  • Confusion or agitation
  • Loss of appetite
  • Paranoia
  • Abnormal emotional responses

In the final stages, people with vCJD won't know where they are and need care all the time. People often die from pneumonia or respiratory failure as their lungs stop working and they can't breathe.

There's no way to know for sure a person has variant CJD until you look at their brain tissue, usually after death. But it's possible to look for it in a brain biopsy. vCJD is very rare, but doctors may suspect it when you have:

  • Early death
  • Psychiatric symptoms
  • Persistent pain
  • Dementia and other signs including loss of coordination and visual changes
  • Illness for more than 6 months
  • No evidence of another disease to explain the illness
  • No history of classic CJD in your family or a prion protein gene mutation

A doctor will run tests to see if your symptoms could be explained by classic CJD or another condition. Tests may include:

  • MRI scans of your brain
  • EEG recordings of your brain activity
  • Lumbar puncture to test your cerebrospinal fluid
  • Blood tests
  • Biopsy of your tonsils to look for prions found in vCJD
  • Genetic tests to see if you may have a hereditary or genetic prion disease
  • Brain biopsy

Doctors don't have any way to treat vCJD or other prion diseases. Treatment is aimed at managing symptoms and keeping you comfortable. Medicines to help with vCJD-related symptoms include:

  • Antidepressants
  • Sedatives
  • Painkillers

A person with any type of CJD, including vCJD, may want an advance directive to say what kind of treatment they want when the disease gets worse. It will say what kind of medicines they want to take and whether they'd want a tube to help them eat or breathe.

The best way to prevent vCJD is to prevent cows from getting BSE. Countries have taken steps to control and prevent mad cow disease and vCJD, which include:

  • BSE testing
  • Killing sick animals
  • Banning materials that are a risk for transmitting BSE in animal and human food and other products

To make sure you don't get vCJD, you could avoid eating beef in countries where BSE is present. If you do eat beef, you could eat solid pieces such as steaks and avoid burgers or sausages containing ground meat that may be more likely to have prions in it. You can't get vCJD from drinking milk.

There's some chance you could get vCJD from donor blood or blood products from an infected person. The risk is probably very small. To protect against this, the FDA defers blood donors who have:

  • Spent a lot of time in countries with more BSE
  • Used cow insulin from the U.K.
  • Received a blood transfusion in the U.K. or France after 1980

Mad cow disease or BSE is a disease cattle can get from infectious agents called prions. The human version, called vCJD, can spread when people eat beef contaminated with brain or spinal cord tissue from an infected cow, or if they receive blood from an infected person. While control measures have made BSE less common and vCJD is very rare, it's hard to diagnose and there's no treatment for the disease, which is fatal.

  • Does cooking food kill the prion that causes mad cow disease?

Common methods to get rid of disease-causing organisms in food, such as heating, do not affect prions. You can't get rid of prions with alcohol, acid, boiling water, high heat, or radiation.

  • Is it possible to get vCJD from eating food purchased in the U.S.?

It's extremely unlikely. To prevent mad cow disease from entering the country, since 1989, the federal government has banned imports of certain types of animals from countries where mad cow disease has been reported. This ban includes meat products used in human, animal, and pet foods. Also, banning high-risk animals from entering the food supply and the removal of central nervous system tissue from the food supply help ensure that BSE is not a risk in the U.S.

  • Can you get vCJD from drinking milk from an infected cow?

Milk and milk products are not believed to pose any risk for transmitting vCJD. Experiments have shown that milk from cows infected with mad cow disease doesn't cause infections.

  • What about other products made from cow byproducts?

The FDA doesn't allow materials from cattle in human food, dietary supplements, or cosmetics. The materials that are banned include the brain, skull, eyes, spinal cord, and other parts of the nervous system from cattle older than 30 months as well as the tonsils or small intestine from all cattle. You also can't use material from a disabled cow or cattle that hasn't passed inspection.

  • What is the current risk of vCJD to Americans traveling abroad?

According to the CDC, the current risk of acquiring vCJD appears to be extremely small. But the precise risk in any specific country is hard to know.

  • What other countries have reported cases of mad cow disease?

BSE was mostly in the U.K. But cases have been reported in other countries, including Ireland, Switzerland, France, Liechtenstein, Luxembourg, Netherlands, Portugal, Denmark, Canada, and the U.S.

  • Can other animals get BSE?

Yes, other animals can get their own versions of BSE. Similar illnesses infect sheep, goats, mink, deer, elk, and house cats. 

  • Do hunters need to worry about getting BSE from eating wild animals?

Deer, moose, and elk can get a form of BSE called chronic wasting disease (CWD). Signs of a sick animal are stumbling, lowered head, droopy ears, and weakness. But there are no known cases of CWD passing from animals to people. You should still take precautions, such as not shooting, handling, or eating an animal that's acting sick or abnormal; avoiding contact with brain and spinal tissues; and processing your animals individually (not with meat from other animals).