Bovine Spongiform Encephalopathy (BSE)

Bovine spongiform encephalopathy (BSE), popularly known as ‘mad cow disease,’ belongs to the group of diseases previously known as the subacute, transmissible, spongiform encephalopathies and now often referred to as prion diseases. The clinical signs are more readily detected in the early stages by those familiar with the individual cow's habits, such as herdsmen, who might detect subtle changes in behavior. Subsequently, the signs may be obvious to all, although the term ‘mad’ is not a sound description of all cases. The principal signs are changes in mental status exhibited as apprehension, frenzy, and nervousness of doorways; changes in sensation, notably hyperesthesia to sound and touch; and abnormalities of posture and movement, particularly low head carriage, hindlimb ataxia, tremors, and falling. The duration of signs is 7 days to more than 1 year but commonly 1 or 2 months. Prime beef cattle reared for meat are killed at approximately 2 years and 6 months to 3 years of age on average, well below the age at which clinical BSE usually develops. Nevertheless, some of these animals, if they have been exposed to infection in feed, incubate the disease at the time of slaughter. BSE is preventable through the elimination of BSE-contaminated feed.