Scrapie
From Wikipedia, the free encyclopedia
Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats.[1] It is one of several transmissible spongiform encephalopathies (TSEs), which are related to bovine spongiform encephalopathy (BSE or "mad cow disease") and chronic wasting disease of deer. Like other spongiform encephalopathies, scrapie is caused by a prion.[2] Scrapie has been known since the 18th century (1732) and does not appear to be transmittable 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 itching sensation in the animals. Other symptoms include excessive lip-smacking, strange gaits, and convulsive collapse.[3]
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. Recent studies suggest that prions may be spread through urine and persist in the environment for decades.[4]
An experiment has shown that lambs risk being infected through milk from infected ewes. [5] but the lambs in the experiment also infected each other, making it difficult to assess the chance of infection. The experiment did not continue long enough to show that the lambs developed symptoms, merely that the prion was present in the body.
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.[6]
Out of fear of BSE, many European countries banned some traditional sheep or goat products made without removing the spinal cord such as smalahove and smokie.[7]
[edit] See also
[edit] References
- ^ Detwiler LA (1992). "Scrapie". Rev. - Off. Int. Epizoot. 11 (2): 491–537. PMID 1617202.
- ^ Hunter N (2007). "Scrapie: uncertainties, biology and molecular approaches". Biochim. Biophys. Acta 1772 (6): 619–28. doi:. PMID 17560089.
- ^ Foster JD, Parnham D, Chong A, Goldmann W, Hunter N (2001). "Clinical signs, histopathology and genetics of experimental transmission of BSE and natural scrapie to sheep and goats". Vet. Rec. 148 (6): 165–71. PMID 11258721.
- ^ Detwiler LA, Baylis M (2003). "The epidemiology of scrapie". Rev. - Off. Int. Epizoot. 22 (1): 121–43. PMID 12793776.
- ^ Konold, Moore, Bellworthy, Simmons, "Evidence of scrapie transmission via milk", BMC Veterinary Research 2008, 4:16 doi:10.1186/1746-6148-4-16
- ^ O'Rourke KI, Duncan JV, Logan JR, et al (2002). "Active surveillance for scrapie by third eyelid biopsy and genetic susceptibility testing of flocks of sheep in Wyoming". Clin. Diagn. Lab. Immunol. 9 (5): 966–71. doi:. PMID 12204945.
- ^ Heim D, Kihm U (2003). "Risk management of transmissible spongiform encephalopathies in Europe". Rev. - Off. Int. Epizoot. 22 (1): 179–99. PMID 12793779.
[edit] External links
- Article about scrapie and the aforementioned diagnostic test
- UK government scrapie information
- UK government National Scrapie Plan
- Scrapie research at the Institute for Animal Health (UK)
- Sheep genetics research at the Institute for Animal Health (includes photo of a sheep with scrapie)
- Scrapie in the United States
- US Department of Agriculture video of infected sheep demonstrating Hopping Gait
|
||||||||
