Prion

Prion, microscopic particle that produces a fatal disease in goats and sheep. Prions are linked to scrapie, a disorder that attacks and destroys the central nervous systems of the grazing animals, but scientists do not fully understand how the disease is caused. It is believed that prions contain an excess of protein that disrupts normal cell activity in infected animals and might possibly affect humans as well. Stanley Prusiner, who discovered prions, received the Nobel Medicine prize in 1997.