Scrapie
Scrapie is a transmissible spongiform encephalopathy in sheep and goats. It is caused by a prion form of PrP, known as PrPres. The specific isoform in scrapie is known as PrPSc. Prions multiply by causing normally folded proteins of the same type to take on their abnormal shape, which then go on to do the same, in a kind of chain reaction. These abnormal proteins are gradually accumulated in the body, especially in nerve cells, which subsequently die. It is currently unknown (but very likely), if scrapie can cross the species barrier and infect humans. Scrapie infected sheep will scrape off their fur, which is the origin of the name. Scrapie usually affects sheep 3 to 5 years of age, due to its long incubation period. The primary mode of transmission is from mother to lamb through ingestion of placental or allantoic fluids. The condition is always fatal. Symptoms including repetitive scraping, ataxia, lesions, weight loss, anorexia, lethargy, and death. If scrapie infected sheep are used in meat and bone meal, if fed to cows, it can cause bovine spongiform encephalopathy.
