PRPc is present in neuronal and some extra-neuronal cells. In prion encephalopathies, there is progressive neurodegeneration with characteristic spongiform change and deposition of abnormal PRP, designated PRPsc in brain. The difference between PRPc and PRPsc is one of shape, the pathogenic form having a high percentage of beta pleated structure. The hallmarks of these disorders are their long incubation period, transmissibility, usually to laboratory animals by intracerebral or parenteral routes, and the resistance of the agent to inactivation. The nature of the agent is controversial.
Current evidence favours it being entirely glycoprotein, with no proof of viral nucleic acid.
The agent is not inactivated by normal disinfectants, sterilizing procedures such as routine autoclaving and ultraviolet radiation. Since 1986, BSE in cattle and other bovidae species and Feline Spongiform Encephalopathy in domestic and captive wild cats are attributed to the same common source. There was no epidemiological evidence to support a link between CJD and any animal spongiform encephalopathy prior to 1996 and the concept of a species barrier was accepted. BSE was recognized in 1986 in the UK, and was attributed to inclusion of scrapie-contaminated sheep brain, in meat and bone meal fed to cattle. Alterations in the previous rendering system probably allowed active PRPsc to get into the feed.