A prion is a small infectious particle, which resist inactivation by procedures that modify nucleic acids. Transmissible spongiform encephalopathies (TSEs also known as prion diseases) are a group of progressive conditions that affects the brain and nervous system of humans and animals and are transmitted by prions. Unlike other kinds of infectious diseases that are spread by microbes, the infectious agent in TSEs is a specific protein called prion protein (PrP). TSEs are unique diseases in that they can be inherited, occur spontaneously (sporadic TSE) or can be spread through infection. The clinical signs of the disease in humans vary, but commonly include personality changes, psychiatric problems such as depression, lack of coordination and/or an unsteady gait (ataxia). Patients also may experience involuntary jerking movements called myoclonus, unusual sensation, insomnia, and confusion or memory problems. In the later stages of the disease, patients may have severe mental impairment (dementia) and may lose the ability to move or speak. Well known prion diseases include scrapie (in sheep and goat), bovine spongiform encephapathy (BSE or mad cow disease) and Creutzfeldt- Jakob disease (CJD). Less well known prion diseases include the transmissible mink encephalopathy (TME) (in mink), chronic wasting disease (CWD) (in mule, deer and elk), feline spongiform encephalopathy (FSE) (in cats), Gerstmann-Straussler-Scheinker syndrome (GSS), Alpers syndrome, and fatal familial insomnia (FFI). Six of these affect humans: CJD, GSS, FFI, mad cow disease known as (new) variant CJD, (nvCJD), Alpers syndrome and kuru. These conditions form a spectrum of diseases with overlapping signs and symptoms. There is currently no treatment that can cure or control TSEs.
African Journal of Clinical and Experimental Microbiology Vol. 9 (1) 2008: pp. 38-52