Bovine Spongiform Encephalopathy (Mad Cow Disease)

On December 23, 2003, the first confirmed case of Bovine Spongiform Encephalopathy or BSE, which is commonly known as Mad Cow Disease, was found on a Washington state dairy.

What is BSE?

Bovine Spongiform Encephalopathy (BSE), aka Mad Cow Disease, is a slowly progressing fatal disease that affects the central nervous system in cattle. The disease is believed to be caused by an abnormal or altered protein called a "prion" in the brain. The disease is found almost exclusively in cattle over 2 years old. The incubation period for this disease ranges from 2-8 years and is always fatal. There is no vaccination available to prevent this disease and there currently is no way to test live cattle for the disease. BSE testing currently is conducted only on brain tissue from slaughtered cattle.

Why all the concern?

The reason there is such concern about this disease is the possible link between BSE and a rare human disease called Variant Creutzfeldt-Jakob Disease (vCJD). vCJD is a disease of the central nervous system of humans with similar symptoms to BSE. Recent research in England where the disease has been found, supports an association between vCJD and the consumption of products contaminated with nervous system tissue of BSE cattle. The BSE agent has not however, been found in the meat or muscle tissue of infected cattle.

How is the disease transmitted?

The disease is believed to have been transmitted through the feeding of animal by-product feeds, such as meat and bone meal, made from sheep infected with scrapie (a similar disorder in sheep) or from cows with BSE. FDA banned the feeding of animal by-product feeds to cattle in August 1997 to prevent transmission of this disease in the U.S. Also imports of live cattle and cattle products have been banned from countries known to have BSE since 1989.

Are we testing our cattle for BSE?

Since 1990, USDA has tested 57,352 brain specimens (as of Sept 30, 2003) from cattle displaying any possible symptoms of BSE and the cow in Washington was the very first to test positive. USDA has been closely monitoring for this disease for 13 years.

Is our beef safe for the consumer?

The US Secretary of Agriculture, Ann Veneman gave the following reasons why Americans can be confident in the safety of U.S. beef:

  • The BSE agent is not found in meat like steaks or roasts. It is only found in central nervous system tissue, such as, brain or spinal cord.
  • All U.S. cattle are inspected by a USDA Inspector or veterinarian prior to harvest. Animals with any signs of neurological disorder are tested for BSE.
  • BSE affects older cattle, typically over 30 months of age. The vast majority of the cattle going to market in the U.S. are less than 24 months old.
  • The U.S. began a surveillance program for BSE in 1990 and was the first country without the disease within its borders to test cattle for the disease. The surveillance system targets all cattle with any signs of neurological disorder as well as those over 30 months of age and animals that are unable to walk.
  • The U.S. banned imports of cattle and bovine products from countries with BSE beginning in 1989.
    The only way BSE spreads is through contaminated feed. The U.S. Food &Drug Administration in 1997 instituted a ban on feeding ruminant-derived meat and bone meal supplements to cattle. This is a firewall that prevents the spread of BSE to other animals if it were present in the U.S.

* The above information was compiled by Douglas Mayo, Extension Ag Agent in Jackson County.

More Information

BSE is a chronic degenerative disease affecting the central nervous system of cattle, affected animals display changes in temperament such as nervousness, aggression, in coordination. BSE belongs to a family of diseases known as transmissible spongiform encephalopathies (TSEs) which have been around for years. Other TSEs include scrapie in sheep and goats, chronic wasting disease of deer and elk, and Creutzfeld-Jakob Disease (CJD) in humans.

The BSE disease first appeared in Great Britain in 1986 and has since affected over 178,000 cattle worldwide. The epidemic in Great Britain apparently peaked in 1993 and has since been on the decline due to eradication efforts. It is suspected that the cause of BSE in Great Britain involved animal feed containing contaminated meat and bone meal as a protein source. This practice has since been banned in Europe and the United States.

Cattle affected by BSE have a progressive degeneration of the nervous system. The incubation period or time from when an animal becomes infected until it shows signs of the disease is from 2 to 8 years. After the onset of the disease the animal dies within 2 weeks to 6 months. Most cases in Great Britain have occurred in dairy cattle which were between 3 and 6 years old.

Scientific evidence has found that BSE does not spread between cattle or from cattle to other animal species. The only known way to spread the disease between cattle is through consumption of animal by-products from a contaminated animal. This practice was banned in the U.S. in August of 1997. 

The United States Department of Agriculture, Animal and Plant Health Inspection Service began restrictions on importing live ruminants from countries where BSE was known to exist back in 1989. The restrictions have been tightened several times and in 2000 grew to include a ban of all imports of rendered animal protein products from Europe.

An extensive surveillance program has been conducted in the United States, and the USDA had a formal response plan ready if BSE was found in the U.S. The plan can be viewd in pdf format: Bovine Spongiform Encephalopathy (BSE) Response Plan Summary.