bovine spongiform encephalopathy (BSE)

bovine spongiform encephalopathy (BSE)

a prion disease of cattle, also known, but mis-named, as mad cow disease. The disease has a long incubation period and occurs at a modal age of approximately 5 years with a clinical course of several weeks. Principal clinical signs are changes in sersorium and temperament and behavior, posture and movement especially manifest by ataxia, and in dairy cattle, a fall in milk production. There is no antemortem diagnostic test. Most affected cattle are culled because of behavioral abnormalities before major clinical disease.

The disease emerged in the mid 1980s in the United Kingdom and epidemiological studies showed it was associated with the feeding of meat and bone meal to affected animals when they were calves. It is assumed that the meat and bone meal were contaminated by a scrapie strain capable of transmitting to cattle, possibly as a result of a change in the method of processing meat and bone meal that preceded the outbreak, but the origin of the BSE prion is not clear. Other animal species, including exotic zoo ungulates fed infected meat and bone meal and zoo cats fed culled cattle and domestic cats (but not dogs) fed canned food containing infected meat products developed a transmissible spongiform encephalopathy (TSE). A small proportion of humans, relative to those that must have been exposed by consumption of infected material developed a TSE called variant Creutzfeldt-Jakob disease (vCJD).

The outbreak of BSE in the UK peaked in the early 1990s following the ban of feeding meat and bone meal. International movement of cattle and meat and bone meal prior to the recognition of the disease in the UK, and illegal movement subsequently, resulted in the spread of this infection to many countries— mostly recognized in Europe but mainly unknown in Asia. The disease in cattle can be eliminated by a strict ban and control on the feeding of ruminant animal products to ruminants. The risk of disease in humans eventually can be obviated by imposing and enforcing the feeding ban to cattle (above) but also by avoiding consumption by humans of meat from cattle over 30 months of age. Several countries, for reasons of consumer confidence, test all cattle for BSE before releasing the carcass for consumption. See also scrapie.