11 Bovine Spongiform Encephalopathy and Related Diseases

Abstract

In Great Britain, a previously unrecognized neurologic disease in cattle was first defined in 1986, on the basis of a constellation of clinical signs associated with characteristic pathologic changes in the brain (Wells et al. 1987). There was the insidious onset of altered behavior (either fear or sometimes aggressive responses), ataxia (incoordinated gait with falling), and dysesthia or reflex hyperesthesia (abnormal responses to touch and sound). The relentless progression of these symptoms made it impossible to handle animals, requiring slaughter within 1–6 months (Wilesmith et al. 1988). Histologically, the brain exhibited spongiform lesions and astrogliosis (Wells et al. 1987). It was immediately recognized (Wells et al. 1987) that the lesions were similar to those characteristic of transmissible spongiform encephalopathies (TSEs) or prion diseases in other species, specifically scrapie of sheep, the prototype of the TSEs. In retrospect, cases of BSE had been seen in England as early as 1985, but probably not before that year. This new disease was made statutorily notifiable (Anonymous 1996a; Wilesmith 1996a) and the numbers of cases continued to increase each month, indicating the onset of a major epidemic (Fig. 1).

EPIDEMIOLOGY OF BSE
The United Kingdom
The advent of a new prion disease in epidemic form led to a detailed investigation of its possible cause. An important clue was offered by mapping of the cases occurring within the first 18 months of the outbreak (Wilesmith 1991), which showed that they were widely distributed throughout much of England. The same pattern is reflected in Figure...