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|(unranked)||Mammalian prion
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|(unranked)||Scrapie prion
Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies (TSEs), which are related to bovine spongiform encephalopathy (BSE or "mad cow disease"). Like other spongiform encephalopathies, scrapie is believed to be caused by a prion. Scrapie has been known since the 18th century and does not appear to be transmissible to humans.
The name scrapie is derived from one of the symptoms of the condition, wherein affected animals will compulsively scrape off their fleece against rocks, trees or fences. The disease apparently causes an uncontrollable itching sensation in the animals. Other symptoms include excessive lip-smacking, strange gaits, and convulsive collapse.
Scrapie is infectious and transmissible among similar animals, and so one of the most common ways to contain scrapie (since it is incurable) is to quarantine and destroy 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 these are active areas of research.
In the United Kingdom, the government has put in place a National Scrapie Plan, which encourages breeding from sheep that are genetically more resistant to scrapie. It is intended that this will eventually reduce the incidence of the disease in the UK sheep population. Scrapie occurs in Europe and North America, but to date Australia and New Zealand (both major sheep-producing countries) are scrapie-free.
A test is now available which is performed by sampling a small amount of lymphatic tissue from the third eyelid.
Out of fear of scrapie, many European countries banned some traditional sheep or goat products made without removaing the spinal cord such as smalahove and smokie.
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