Prion is defined as a disease-causing agent and an infectious particle that is neither bacterial nor fungal nor viral and contains no genetic material. A Prion is a protein that occurs normally in a harmless form.
By folding into an aberrant shape, the normal Prion turns into a rogue agent. It then coopts other normal Prions to become rogue Prions. Prions have been held responsible for a number of Degenerative brain diseases that include Scrapie that is a fatal disease of sheep and goats Mad cow disease Creutzfeldt-Jacob disease, Fatal familial insomnia, Kuru which is an unusual form of hereditary Dementia known as Gertsmann-Straeussler-Scheinker disease, and possibly some cases of Alzheimer's disease. Creutzfeldt-Jakob disease refers to an extremely rare condition that causes dementia; a neurological disease transmitted from animals to humans that leads to dementia and death resulting from abnormal protein accumulations in the brain. Dr. Stanley B. Prusiner received the 1997 Nobel Prize in Physiology or Medicine for his discovery of Prions.