Scrapie

Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats.cite journal
author=Detwiler LA
title=Scrapie
journal=Rev. - Off. Int. Epizoot.
volume=11
issue=2
pages=491–537
year=1992
pmid=1617202
doi=] 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.cite journal
author=Hunter N
title=Scrapie: uncertainties, biology and molecular approaches
journal=Biochim. Biophys. Acta
volume=1772
issue=6
pages=619–28
year=2007
pmid=17560089
doi=10.1016/j.bbadis.2007.04.007
url=http://linkinghub.elsevier.com/retrieve/pii/S0925-4439(07)00106-8] 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.cite journal
author=Foster JD, Parnham D, Chong A, Goldmann W, Hunter N
title=Clinical signs, histopathology and genetics of experimental transmission of BSE and natural scrapie to sheep and goats
journal=Vet. Rec.
volume=148
issue=6
pages=165–71
year=2001
pmid=11258721
doi=]

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.cite journal
author=Detwiler LA, Baylis M
title=The epidemiology of scrapie
journal=Rev. - Off. Int. Epizoot.
volume=22
issue=1
pages=121–43
year=2003
pmid=12793776
doi=]

An experiment has shown that lambs risk being infected through milk from infected ewes. [Konold, Moore, Bellworthy, Simmons, "Evidence of scrapie transmission via milk", BMC Veterinary Research 2008, 4:16 doi:10.1186/1746-6148-4-16] 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.cite journal
author=O'Rourke KI, Duncan JV, Logan JR, "et al"
title=Active surveillance for scrapie by third eyelid biopsy and genetic susceptibility testing of flocks of sheep in Wyoming
journal=Clin. Diagn. Lab. Immunol.
volume=9
issue=5
pages=966–71
year=2002
pmid=12204945
doi=10.1128/CDLI.9.5.966-971.2002
url=http://cvi.asm.org/cgi/pmidlookup?view=long&pmid=12204945] 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.cite journal
author=Heim D, Kihm U
title=Risk management of transmissible spongiform encephalopathies in Europe
journal=Rev. - Off. Int. Epizoot.
volume=22
issue=1
pages=179–99
year=2003
pmid=12793779
doi=]

See also

* Kuru
* Transmissible mink encephalopathy
* Creutzfeldt-Jakob disease

References

External links

* [http://www.wsu.edu/NIS/Universe/SheepSt.html Article about scrapie and the aforementioned diagnostic test]
* [http://www.defra.gov.uk/animalh/bse/bse-science/level-4-scrapie.html UK government scrapie information]
* [http://www.defra.gov.uk/animalh/bse/othertses/scrapie/nsp/index.html UK government National Scrapie Plan]
* [http://www.iah.bbsrc.ac.uk/primary_index/current_research/groups/bruce_mabbott.htm Scrapie research at the Institute for Animal Health (UK)]
* [http://www.iah.bbsrc.ac.uk/primary_index/current_research/groups/hunter.htm Sheep genetics research at the Institute for Animal Health] (includes photo of a sheep with scrapie)
* [http://www.aphis.usda.gov/vs/nahps/scrapie/ Scrapie in the United States]
*US Department of Agriculture [http://www.aphis.usda.gov/animal_health/videos/hopping.mpg video] of infected sheep demonstrating Hopping Gait