• 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 ± Crossing the “species barrier” • Scrapie in sheep → Mink was fed with meat from scrapie sheep → TME in mink (carnivorous); Rendering of scrapie sheep to make dietary supplement (powder) for cows → BSE in cows 3 Modes of Prion Disease Transmission ± Inherited form: Autosomal dominant mutations in the prion gene (conversion of mutant PrP C into PrP Sc ); e.g. Familial CJD, GSS, FFI ± Acquired form • Ingestion; protease resistant core is absorbed from the digestive tract and goes into the circulation, and eventually gets to the brain; e.g. Kuru, vCJD • Iatrogenic: contaminated medical instrument (e.g. electrodes); growth hormone products from the pituitary glands of cadavers died from CJD; cornea transplant ± Sporadic form: spontaneous generation of PrP Sc Clinical features ±
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