Scrapie

Scrapie (ˈskreɪpi) is a fatal, degenerative disease affecting the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies (TSEs), and as such it is thought to be caused by a prion. Scrapie has been known since at least 1732 and does not appear to be transmissible to humans. However, new studies suggest a link between scrapie and sporadic CJD. The name scrapie is derived from one of the clinical signs of the condition, wherein affected animals will compulsively scrape off their fleeces against rocks, trees or fences. The disease apparently causes an itching sensation in the animals. Other clinical signs include excessive lip smacking, altered gaits and convulsive collapse. Scrapie is infectious and transmissible among conspecifics, so one of the most common ways to contain it (since it is incurable) is to quarantine and kill those affected. However, scrapie tends to persist in flocks and can also arise apparently spontaneously in flocks that have not previously had cases of the disease. The mechanism of transmission between animals and other aspects of the biology of the disease are only poorly understood, and are active areas of research. Recent studies suggest prions may be spread through urine and persist in the environment for decades. Scrapie usually affects sheep around three to five years of age. The potential for transmission at birth and from contact with placental tissues is apparent. The disease has been notifiable in the EU since 1993, but unlike BSE, there was no evidence as of 1999 to suggest that scrapie is a risk to human health. In July 2003, a Canadian Food Inspection Agency officer said that while scrapie shows up every year on Canadian farms, "We've had a lot of experience with scrapie and there's never been a link between scrapie and human illness." As of 2004, the USDA made no mention of scrapie in its Sheep and Goats Death Loss circular. Historically, scrapie had been considered to be an animal health issue.