A usually fatal disease of sheep and goats, marked by chronic itching, loss of muscular coordination, and progressive degeneration of the central nervous system.
[From SCRAPE (from the scraping of itching parts of the skin against objects).]
scrapie
Dictionary:
scra·pie (skrā'pē, skrăp'ē)  |
n.
A usually fatal disease of sheep and goats, marked by chronic itching, loss of muscular coordination, and progressive degeneration of the central nervous system.
A usually fatal disease of sheep and goats, marked by chronic itching, loss of muscular coordination, and progressive degeneration of the central nervous system.
| 5min Related Video: scrapie |
| Sci-Tech Encyclopedia: Scrapie |
A transmissible, usually fatal disease of adult sheep characterized by degeneration of the central nervous system. The disease is known in Great Britain, France, Belgium, Iceland, the United States, Canada, and northern India. Scrapie has certain similarities with kuru, a human disease in New Guinea, and mink encephalopathy.
Scrapie affects both sexes and is insidious in its onset, starting with hyperexcitability and progressive itch. Later, loss of wool occurs when the animal rubs against fixed objects or bites and nibbles its skin. Some animals do not rub but are either nervous and tremble when approached or appear sleepy. Incoordination of gait is constant and usually more evident in the hindquarters. In the final stages the sheep, being unable to stand, lie down, become emaciated, and die. See also Prion disease.
| Veterinary Dictionary: scrapie |
An infectious, fatal, chronic disease of sheep and goats with clinical signs of pruritus, abnormalities of gait, recumbency and a long illness of about 6 months. A transmissible spongiform encephalopathy. The incubation period is at least 2 years. Susceptibility to scrapie is genetically determined and control programs are developed to select scrapie resistant sheep.
- s. agent — scrapie is caused by an agent that acts like a virus but does not have the physical characteristics of one. Despite intensive study the true nature of the scrapie agent has not been defined; it is not a conventional virus or a viroid and current studies suggest that it may be a small-molecular-weight, ‘self-replicating’ basic protein for which the term prion has been proposed. The scrapie agent is of interest beyond its role as a rare pathogen for sheep in that it is a prototype of a new class of infectious agents responsible for a number of slow degenerative central nervous system diseases of humans and other animal species. See scrapie, prion, bovine spongiform encephalopathy, feline spongiform encephalopathy.
- s.-associated fibrils — characteristic proteinaceous fibrils in the neurons of sheep with scrapie; the fibrils consist of membrane glycoprotein the DNA of which exists in the patient's brain cells. The glycoprotein accumulates because horizontally acquired scrapie agent induces transcription of the related host chromosomal gene and converts it to a polymerized proteinase-resistant fibrillar form.
- s. eradication programs — most countries with scrapie have established scrapie eradication or scrapie monitoring schemes based on genotyping. According to the 2003 EU-Directive 2003/100/EC every member state has to establish a breeding program based on scrapie resistance.
- s. eyelid test — the presence of the scrapie agent in lymphoid tissue allows its detection in the lymphoid tissue of the third eyelid in live sheep. This is in contrast to the BSE agent in cattle which does not occur in lymphoid tissue and for which there is no ante mortem test.
- s. genotyping — susceptibility to scrapie is associated with polymorphisms in the ovine prion protein (PrP) gene at codons 136, 154 and 171. Genotyping can establish resistant sheep and genotype testing for susceptibility to scrapie is a key element of the scrapie eradication program.
| Wikipedia: Scrapie |
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 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 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]
Contents |
Uptake of prions
The protein enters through the intestines or through cuts in the skin. The prions cause normal proteins of the sheep to fold into the wrong shape. These proteins are gradually accumulated in the body, especially in nerve cells which subsequently die. When the prions are absorbed through the intestines, they first appear in the lymph nodes, especially in Peyer's patches at the small intestine[5].
An experiment has shown that lambs risk being infected through milk from infected ewes[6]. But the lambs in the experiment also infected each other, making it difficult to assess the risk 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.
Preventive action
A test is now available which is performed by sampling a small amount of lymphatic tissue from the third eyelid.[7]
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.
Breeds such as cheviot sheep and suffolk are more susceptible to scrapie than other breeds.[8] Specifically, this is determined by the genes coding for the naturally occurring prion proteins. The most hardy sheep have a double set of "ARR" alleles, while sheep with the "VRQ" allele are the most susceptible.[9] A simple blood test reveals the allele of the sheep and many countries are actively breeding away the VRQ allele.
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.[10]
See also
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. http://linkinghub.elsevier.com/retrieve/pii/S0925-4439(07)00106-8.
- ^ 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.
- ^ Tarmen viktig for skrapesyke - forskning.no [1]
- ^ 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. http://cvi.asm.org/cgi/pmidlookup?view=long&pmid=12204945.
- ^ Eddie Straiton, "Sheep Ailments - recognition and treatment", 7th edition (2001) ISBN 1-86126-397-X
- ^ Synnøve Vatn, Lisbeth Hektoen, Ola Nafstad "Helse og Velferd hos sau" 1. utgave, Tun Forlag (2008) ISBN 978-82-529-3180-8
- ^ Heim D, Kihm U (2003). "Risk management of transmissible spongiform encephalopathies in Europe". Rev. - Off. Int. Epizoot. 22 (1): 179–99. PMID 12793779.
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
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