Prion Disease

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  • Prion diseases are also knowns as transmissible spongiform encephalopathies (TSEs).
  • They are a group of fatal neurodegenerative diseases which occur in a number of species, including man.
    • For example:
      • Bovine spongiform encephalopathy (BSE) in cattle
      • Scrapie in sheep
      • Chronic wasting disease in elk and deer
      • Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), fatal familial insomnia (FFI) and kuru in man
  • TSEs have a long incubation period, making them difficult to diagnose.

feline spongiform encephalopathy has been found within cats in the UK.


  • The aetiology of prion diseases is still highly controversial.
    • However, an abnormal isoform of the host-encoded prion protein (PrP) is seen in the brains of affected animals.
      • The normal host PrP changes its structure into the disease-associated form PrPSc.
    • The abnormal proteint (PrPSc) accumulates as amyloid fibrils in nervous tissue.
  • The agent appears to be highly resistant.



  • Prion diseases cause NO GROSS LESIONS.


  • TSEs typically cause what is known as the "microscopic triad":
    1. Spongiform change.
      • Vacuolation of neurons.
      • Particularly in nuclei.
    2. Astrogliosis
    3. Amyloid plaques
      • These are not always seen.