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There is currently minimal risk of transmitting the degenerative brain disorder known as “mad cow disease” (bovine spongiform encephalopathy [BSE]) to humans in the United States, according to a recent article in The Journal of the American Medical Association (JAMA).

Litjen Tan, Ph.D., and colleagues at the American Medical Association's Council on Scientific Affairs in Chicago, reviewed current scientific literature on BSE and related diseases.

The council presented its report and recommendations to the AMA House of Delegates, which adopted the recommendations at its 1998 Annual Meeting.

BSE is a disease in cows that belongs to a family of chronic, progressive and always fatal neuro-degenerative disorders called transmissible spongiform encephalopathies (TSEs). Other TSEs include the sheep disease, scrapie, and the human brain disease, Creutzfeldt-Jakob disease (CJD). Researchers have hypothesized that an infectious protein known as a prion is the agent responsible for TSEs.

BSE was first diagnosed in 1986. It begins with signs of anxiety, restlessness and aggressive behavior, leading to the name “mad cow disease.” The authors conclude that the risk of contracting a human TSE from cattle in the United States is minimal for the following reasons:

• BSE has not been shown to exist in the United States.
• Adequate regulations exist to prevent entry of foreign sources of BSE into the United States.
• Adequate regulations exist to prevent undetected cases of BSE from uncontrolled amplification within the U.S. cattle population.
• Adequate preventive guidelines exist to prevent high-risk bovine material from contaminating products intended for human consumption.

There have been 173,126 cases of BSE in the United Kingdom.

“Unique circumstances in the United Kingdom caused the emergence and propagation of BSE in cattle, including widespread use of meat and bonemeal cattle feed derived from scrapie-infected sheep, and adoption of a new type of processing that did not reduce the amount of infectious prions prior to feeding,” the authors write. “Many of these circumstances do not exist in the United States.”

No cases of BSE have been found in the United States.

In 1995, a new variant form of CJD disease was identified in the United Kingdom. Known as nv-CJD, it occurs among younger people and presents very different clinical and pathologic features from other forms of CJD. As of Jan. 31, there have been 39 cases of nv-CJD in the United Kingdom and one case in France.

“Data suggest that nv-CJD results from transmission of the BSE prion to humans,” the authors write. “In the United Kingdom, human infection with nv-CJD probably resulted from ingestion of BSE-contaminated beef.”

The extent to which the human population might be affected by nv-CJD is still unknown.

The United Kingdom and the European Union have taken steps to minimize the risk of further contamination of cattle with BSE, to eradicate any existing BSE cases, and to eliminate human exposure to the BSE agent.