Scrapie: Difference between revisions

}}</ref>

 

 

==Regulation==

The disease has been notifiable in the EU since 1993, but unlike [[Bovine spongiform encephalopathy|BSE]], there was no evidence as of 1999 to suggest that scrapie is a risk to human health.<ref name="Brown et al., 1987">Brown P, Cathala F, Raubertas RF, Gajdusek DC, Castaigne P (1987) "The epidemiology of Creutzfeldt–Jakob disease: conclusion of a 15-year investigation in France and review of the world literature". ''Neurology'', 37(6):895–904.</ref><ref name="Harries et al.,1988">Harries JR, Knight R, Will RG, Cousens SN, Smith PG, Mathews WB (1988) "Creutzfeldt–Jakob disease in England and Wales, 1980–1984: a case-control study of potential risk factors". ''Journal of Neurology Neurosurgery and Psychiatry'', 51(9):1113–1119.</ref><ref name="Kondo and Kuriowa, 1982">Kondo K, Kuriowa Y (1982). "A case control study of Creutzfeldt-Jakob disease: association with physical injuries". ''Annals of Neurology'', 11(4):377–381.</ref><ref name="WHO, 1999">World Health Organization, 1999. WHO consultation on public health and animal transmissible spongiform encephalopathies: epidemiology, risk and research requirements, with the participation of the Office International des Epizooties. [http://www.who.int/csr/resources/publications/bse/WHO_CDS_CSR_APH_2000]{{dead link|date=December 2021|bot=medic}}{{cbignore|bot=medic}} Accessed 7 March 2005. http://www.who.int/csr/resources/publications/bse/en/whocdscsraph20002.pdf.</ref> 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."<ref name=npnsp/> As of 2004, the [[USDA]] made no mention of scrapie in its ''Sheep and Goats Death Loss'' circular.<ref name="nass">{{cite web| date= 2005-05-06 |title=Sheep and Goats Death Loss | publisher=[[National Agricultural Statistics Service]] |url=https://downloads.usda.library.cornell.edu/usda-esmis/files/hh63sv88v/xk81jp327/9g54xm03j/sgdl-05-06-2005.pdf |access-date=2019-01-22}}</ref>

 

* [[Meat and bone meal]] (MBM), which was suspected to be the source of the BSE in cattle outbreak in the late 1990s, had also been fed to sheep and goats.

* BSE had been transmitted to sheep following experimental oral exposure.

 

==Clinical signs and diagnosis==

 

The signs and effects of scrapie typically appear 2-5 years after infection but may appear afterwards. Once the onset of clinical signs has occurred, sheep typically live for 1-6 months. In some cases, they may live longer, but death is an inevitable consequence of the condition. Signs of scrapie vary between infected individual animals and develop slowly. Due to the nerve cell damage caused by the condition, affected animals may exhibit behavioral changes, tremor, [[pruritus]], and locomotor incoordination.<ref>{{cite web |title=Scrapie |url=https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/nvap/NVAP-Reference-Guide/Control-and-Eradication/Scrapie |website=Animal and Plant Health Inspection Service |access-date=27 February 2023}}</ref>

}}</ref>

 

 

Breeds such as [[Cheviot sheep|Cheviot]] and [[suffolk (sheep)|Suffolk]] are more susceptible to scrapie than other breeds.<ref name=Straiton>Eddie Straiton, "Sheep Ailments - recognition and treatment", 7th edition (2001) {{ISBN|1-86126-397-X}}</ref> Specifically, this is determined by the genes coding for the naturally occurring prion proteins. The most resistant sheep have a double set of ''ARR'' [[allele]]s, while sheep with the ''VRQ'' allele are the most susceptible.<ref name=Helse>Synnøve Vatn, Lisbeth Hektoen, Ola Nafstad "Helse og Velferd hos sau" 1. utgave, Tun Forlag (2008) {{ISBN|978-82-529-3180-8}}</ref> A simple blood test reveals the allele of the sheep, and many countries are actively breeding away the ''VRQ'' allele.

 

===Exposure through contaminated vaccines===

 

===Exposure through contaminated soil===

 

===Transmission summary===

 

Effective methods of inactivating prions in the soil are currently lacking, and the effects of natural degradation mechanisms on prion infectivity are largely unknown. An improved understanding of the processes affecting the mobility, persistence and [[bioavailability]] of prions in soil is needed for the management of prion-contaminated environments. A system for estimating the prion-binding capacity of soil on farms using simple soil analysis may allow an estimate of the prion risk in the environment, and whether altering prion binding by the use of soil amendments may help to mitigate the infectious prions. [[Lichen]]s, specifically, ''[[Parmelia sulcata]]'', ''[[Cladonia rangiferina]]'' and ''[[Lobaria pulmonaria]]'', may have potential for reducing the number of prions because some lichen species contain [[protease]]s that show promise in breaking down the prion. Further work to clone and characterize the proteases, assess their effects on prion infectivity, and determine which component organism or organisms present in lichens produce or influence the protease activity is warranted and is currently under investigation.<ref>{{cite journal|last=Johnson|first=CJ|title=Degradation of the disease-associated prion protein by a serine protease from lichens|journal=PLOS ONE|year=2011|doi=10.1371/journal.pone.0019836|volume=6|issue=5|pages=e19836|display-authors=etal|pmid=21589935|pmc=3092769|bibcode=2011PLoSO...619836J|doi-access=free}}</ref>

* [[Transmissible mink encephalopathy]]

* [[Virino]]

 

== References ==