cattle first recognized in 1986 in the United Kingdom, The epidemic began simultaneously at many geographic locations and was traced to contamination of meat and bone meal (MBM), a dietary supplement prepared from rendering of slaughterhouse offal.

A comparison of data from the United Kingdom with data from relatively low incidence countries, such as Switzerland, indicates that this epidemic has been mainly confined to the United Kingdom because of a unique concatenation of risk factors, including: 1) a high ratio of sheep to cattle; 2) a relatively high rate of endemic scrapie; 3) the heavy feeding of MBM to dairy cattle; and 4) changes in the rendering process used to prepare MBM

A comparison of data from the United Kingdom with data from relatively low incidence countries, such as Switzerland, indicates that this epidemic has been mainly confined to the United Kingdom because of a unique concatenation of risk factors, including: 1) a high ratio of sheep to cattle; 2) a relatively high rate of endemic scrapie; 3) the heavy feeding of MBM to dairy cattle; and 4) changes in the rendering process used to prepare MBM

However, the cases gave no history indicating an unusual exposure to live cattle, to the preparation of beef products, or of dietary exposure to bovine tissues, and it remains to be determined whether they are associated with BSE.