In humans, prion diseases can be divided into several categories based on presumed etiologies [5, 11]: sporadic Creutzfeldt-Jakob disease (CJD), iatrogenic CJD associated with injection or grafting of infected tissue (growth hormone, dura and cornea), variant CJD associated with exposure to bovine spongiform encephalopathy (BSE)-contaminated beef, and genetic/familial prion disease associated with inherited PrP mutations.