A prion has been defined as "small proteinaceous infectious particles which resist inactivation by procedures that modify nucleic acids" (Knight R,2001). The discovery that proteins alone can transmit an infectious disease has come as a considerable surprise to the scientific community. Prion diseases are often called spongiform encephalopathies because of the post-mortem appearance of the brain with large vacuoles in the cortex and cerebellum ( Bruce et al.,1997). Probably most mammalian species develop these diseases. Specific examples include: Scrapie: sheep, TME (transmissible mink encephalopathy): mink, CWD (chronic wasting disease): muledeer, elk, BSE (bovine spongiform encephalopathy): cows. Humans are also susceptible to several prion diseases: CJD: Creutzfeld-Jacob Disease ; GSS: Gerstmann-Straussler-Scheinker syndrome ; FFI: Fatal familial Insomnia ; Kuru ; Alpers Syndrome (Will, 2001).