Updated 7/05/05

Bovine Spongiform Encephalopathy (BSE) is one variety of a group of diseases known as "Transmissible Spongiform Encephalopathies" (TSEs). TSEs cause microscopic holes in the brain, giving it a sponge-like appearance under a microscope. TSEs are always fatal and affect both humans and animals. 

BSE is the type of TSE that occurs in cattle. Scientists believe cattle are infected when they eat feed that contains remnants of infected animals. 

The most common human TSE is Creutzfeldt-Jakob disease (CJD). Scientists believe a new variant form of CJD is caused by consuming the brain and spinal cord of animals infected with BSE. 

On December 23, 2003 a cow was diagnosed with Bovine Spongiform Encephalopathy (BSE) in Washington State. The cow was traced to its origin in Canada. A total of 255 animals that were or could have been from the source herd in Alberta, Canada were identified on 10 premises in Washington, Oregon and Idaho. All 255 animals tested negative for BSE. After this extensive testing and trace back of feed cohorts, USDA officially closed its investigation into the BSE incident in Washington State on Feb. 9 2004.

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Expanded BSE testing

The U.S. Department of Agriculture’s expanded surveillance program for BSE has been underway since June 2004 with a goal to test approximately 268,000 animals by December 2005.

USDA is targeting the highest risk cattle (those 24 months of age and older). Carcasses from tested animals are held and not allowed to enter the food supply until the test results show the samples are negative for BSE.

Washington State University’s Animal Disease Diagnostic Laboratory is one of seven state laboratories conducting testing for USDA’s increased surveillance efforts. When test results are “inconclusive,” the sample is sent to the USDA’s National Veterinary Services Laboratory in Ames, Iowa for confirmatory testing.

According to USDA, “inconclusive results are a normal component of screening tests, which are designed to be extremely sensitive so they will detect any sample that could possibly be positive.”

More information on the surveillance program is available on USDA’s web site.

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