Prions Causing Transmissible Neurodegenerative Diseases

Seven diseases, four of animals and three of humans, are probably caused by prions (Table 12.1). The unusual properties of the infectious pathogens causing scrapie prompted introduction of the term “prion” to distinguish this class of particles from viruses and viroids.1 The slow infectious agents that cause transmissible mink encephalopathy (TME), chronic wasting disease (CWD), and kuru are not well characterized; thus, further knowledge about the properties of these infectious agents must be obtained before they can be firmly classified as prions. Much more is known about the prion particles that cause Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker syndrome (GSS), and bovine spongiform encephalopathy (BSE).2–4 For ease of discussion, all the diseases listed in Table 12.1 are referred to as prion diseases even though a prion etiology must be considered tentative until the molecular properties of each slow infectious agent are well defined.5