Scrapie is a deadly, degenerative and transmissible disease that affects the central nervous system of sheep and goats.
Scrapie has been known since the 18th century. This disease has been present in sheep and goats for centuries and has been observed worldwide, but especially in Western Europe and North America. In French the disease is called Tremblante and in German Traberkrankheit.
The name Scrapie is derived from one of the symptoms. Due to severe itching, sick animals scrape their skin against fences or other fixed objects. Other symptoms are a dry coat and skin, and severe weight loss. Movement disorders can also occur. However, these are not as pronounced as with BSE in cattle; usually only one animal of the herd is affected.
Long incubation time
Scrapie has an incubation period of more than two years. As a result, the disease symptoms are only seen in adult animals. In non-susceptible animals, the pathogen has virtually no chance of causing disease symptoms during their relatively short lives.
There are classical forms and atypical forms of scrapie. Scrapie, like BSE, is a transmissible spongiform encephalopathy (TSE) or prion disease. Prion diseases are very unusual; unlike bacterial, viral or parasitic infections, prion diseases are caused by a protein that is normally present in the host. This protein is known as a prion protein or simply PrP.
Spreading the infection
Scrapie is an infectious disease. The nature of the agent (the prion) that causes Scrapie is not fully understood, and the mode of transmission is not entirely clear. It has been established that the Scrapie agent can survive several years in the environment, that it is relatively resistant to disinfectants and that host genetic (hereditary) factors mainly determine the susceptibility to the disease. In sheep, the assumption is that an important route of horizontal and vertical transmission is via the placental material (afterbirth) of infected ewes during lambing.
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Detection of Prion Protein Particles in Blood Plasma of Scrapie Infected SheepPLoS ONE 7 (2012)5. - ISSN 1932-6203 - 8 p.
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Gene expression profiling en association with prion-related lesions in the medulla oblongata of symptomatic natural scrapie animals.PLoS ONE 6 (2011)5. - ISSN 1932-6203 - 12 p.
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