Bovine spongiform encephalopathy (BSE) and its epidemiology.

Since the recognition of BSE in 1986, over 180,000 cattle in the UK have developed the disease and 1-3 million are likely to have been infected with the BSE agent, most of which were slaughtered for human consumption before developing signs of the disease. The origin of the first case of BSE is unknown, but the epidemic was caused by the recycling of processed waste parts of cattle, some of which were infected with the BSE agent, to other cattle in feed. Control measures have resulted in the consistent decline of the epidemic in the UK since 1992. Cattle and feed exported from the UK have seeded smaller epidemics in other European countries, where control measures were applied later. If the control measures now in place to protect public and animal health are well enforced, the epidemic in cattle should be largely under control and any remaining risk to humans through the consumption of beef should be very small.