Bovine Spongiform Encephalopathy (BSE)

Bovine spongiform encephalopathy (BSE) or ‘Mad Cow Disease” is a chronic, degenerative neurological disease of cattle.  Scientists believe BSE is cased by misfolded proteins, called prions, which build up in tissues of the central nervous system, eventually killing nerve cells.  The prions are resistant to common food disinfection treatments, such as heat, to reduce or eliminate their presence.

BSE In Cattle

Clinical signs include changes in temperament, drooling, itching of the head, fine muscular tremors, moaning, rapid respiratory rate, slow heart rate, incoordination, abnormal postures, abnormal gait, decreased milk production, loss of body condition despite a normal appetite, and death.

The incubation period of BSE ranges from two to eight years and the health of affected animals typically deteriorates over a period of two weeks to six months.  Most cattle affected are between three and six years old.


BSE does not spread from animal to animal or animal to human contact.  It can only be transmitted through feed containing ruminant-derived meat and bone meal from BSE-infected cattle.  The use of such products in cattle feed was banned in the USA in 1997. 

Screening and Testing

Cattle presented for slaughter in the USA are evaluated by the Food Safety and Inspection Service for signs of neurological disease.  The carcasses of suspect cattle are condemned and are not used for human food.  Central nervous system tissue from these animals then undergo a pathologic examination.

No laboratory tests exist to confirm BSE in live cattle.  It is most often diagnosed by a microscopic evaluation of the brain and spinal cord tissue following the animal’s death.

There are not treatments available for cattle affected by BSE.  The disease is uniformly fatal. 

Food Safety Information

The U.S. beef supply is extremely safe.  It is important to remember that BSE is first and foremost an animal disease issue.

The BSE agent is not found in the beef Americans typically consume.  It is found in central nervous system tissue.  The BSE agent has never been found in muscle meat. 

In recent years, USDA has made sweeping changes in slaughter and processing establishments to further reduce any risk to public health. 

For More Information
The Pennsylvania Department of Agriculture BSE Websitedead link
Phone: 717-772-2852

U.S. Department of Agriculture BSE Website
PA USDA-APHIS Phone: 717-782-3442

PA Beef Council Website
Phone: 717-939-7000

National Cattlemen’s Beef Association BSE Website
Phone: 303-694-0305