MAD COW DISEASE
ENCE PHALO PATHIES -- VIRUS
OR PRION DISEASE?
Over 200 years ago farmers in England, Scotland, and France noted that some sheep suffered a progressive loss of balance, shaking, wasting, and severe itching that caused them to rub their hindquarters and flanks against any upright post. The name scrapie, or tremblante in France, was given to this disorder. Owners of healthy flocks recognized that their animals contracted scrapie only after introduction of new breeding stock later found to bear the disease. Eventually sheep exported from England infected herds in Australia, New Zealand, and South Africa. Only extermination of the affected animals stopped scrapie from spreading, but by then it was distributed widely throughout Europe, Asia, and America.
Nearly 100 years later, C. Besnoit ( 1) reported experimental transmission of the same disease by inoculating ewes with brain tissue from a sheep with scrapie. Then, in the 1930s, J. Cuillé ( 2, 3) provided evidence for the first unequivocal transmission of scrapie to healthy sheep and documented that