Prion Diseases of Animals and Humans

Prions are unique infectious agents that result from the conformational conversion of normal host protein PrPC to an abnormal infectious self-templating form of the prion protein, PrPSc. PrPSc accumulation in the host results in a triad of neuropathological signs including vacuolation, gliosis, and neuronal degeneration that inevitably lead to the death of the host. Prion diseases have long incubation periods, are naturally found in animals and humans, and, due to the protein-only nature of the infectious agent, can have sporadic, genetic, or acquired etiologies. Some prion diseases are particularly promiscuous, such as bovine spongiform encephalopathy (BSE), which has crossed species barriers into ungulates, felines, primates, and mink. BSE has also resulted in zoonotic transmission to humans causing variant Creutzfeldt-Jakob disease (CJD). Prions from scrapie of sheep and goats and chronic wasting disease of cervids can persist in the environment for years, are horizontally and vertically transmissible, and have host ranges that are still incompletely described. All prion diseases are inevitably fatal and, to date, effective treatments have not been available. Recent work, however, has led to the development of reliable diagnostic tests that can rapidly detect PrPSc, which hold promise for practical diagnosis of animals and patients.