Prion diseases Flashcards
What causes a prion disease?
The change of normal cellular protein from Prp(C) to PrP(BSE/SC)
Describe the mechanism of prion disease development
List some prion diseases of animals
- Bovine spongiform encephalopathy (mad cow disease)
- Scrapie
What is the incubation period of BSE?
2-8 years
How is BSE transmitted?
- Ingestion of bone-meal contaminated with mutated prion
- Spontaneous mutation (less common in BSE)
Which animals are more prone to infection with BSE?
Young animals (<6 months), but clinical signs do not appear until 3-8 years old
Where do prions from BSE replicate once in the body?
In the Peyer’s patches of the ileum
How does BSE develop (pathogenesis)?
- Ingestion
- Replicates in Peyer’s patches of ileum
- Transported via PNS to CNS
- Accumulates in brain
Can sheep and goats get BSE?
Yes, but much less likely! More likely to suffer from scrapie
What are the different forms of clinical disease of BSE in cattle?
- Neurological disease
- Atypical BSE
Describe the typical clinical signs of neurological BSE
- Gait abnormalities
- Hind limb ataxia and hypermetria
- Hyperresponsive to stimuli
- Tremors
- Behavioural changes - AGGRESSION
- Non-specific signs
Describe the typical clinical signs of atypical BSE
- Inactivity
- Mental dullness
- Low carriage of head
- Kyphosis
- Sudden falling
- Hyper-responsivity to tactile stimuli (but not light or sound)
What are the histopathological changes seen in BSE?
Neuronal vacuolation and non-inflammatory spongiform changes in the grey matter
How do we diagnose BSE?
- Necropsy and histopathology
- Immunoblotting
- Immuno-histochemistry
- ELISA, western blot
Why can we not use serology to diagnose BSE?
As the body recognises the BSE as “self-protein” and so no Ab are made
How do we treat BSE?
We don’t - cull!
List some preventative measures related to BSE control
- OIE reportable
- Cull cohort - any who received same feed
- Specific risk material
- Taken from ALL animals >3 years old
- Entire head with skin and ear tag
- Medulla obongata
- Slaughterhouse
- All animals >72 months
- All emergency slaughters >48 months
- All animals >48 months showing ANY suspected clinical signs
- Taken from ALL animals >3 years old
- Cannot feed bone meal or blood meal
Which sheep are most commonly affected by scrapie?
Cheviots
Suffolk
What is the incubation period of scrapie?
2-5 years
How is scrapie transmitted?
- Neonates - licking and ingesting foetal membranes and fluid
- Direct contact
- Contaminated fomites
- Mutation
What are the typical clinical signs of scrapie in sheep?
- Separation from flock
- Hyper-excitability and hyper-metria
- Ataxia, incoordination, blindndess, convulsions
- Intense pruritus - anorexia
- Death in 2-6 weeks after clinical signs appear
How is scrapie diagnosed?
- Clinical signs
- Immuno-histochemistry
- Histopathology
- Brain and spinal cord
- Western blot
- Immunohistochemistry
Describe the slaughterhouse monitoring of scrapie?
- 10 samples from each farm
- Entire head of animal or brainstem
- Taken from animals >18 months old OR
- From animals with >2 erupted permanent incisors
