Ruminant Neurology 2 pt 2 Flashcards
Bovine Spongiform Encephalopathy
- significance
- similar diseases?
- what is it?
Reportable disease
“Mad Cow” Disease
<><>
Transmissible Spongiform Encephthalopathies:
Kuru – Papua New Guinea
Creutzfeld-Jakob Disease (CJD)
Gerstmann-Straussler-Scheinker syndrome
<><>
Slowly progressive, fatal neurodegenerative disease
B. S. E.
- agent?
- pathogenesis
Prion diseases
Normal prion protein (PrP) – host encoded
membrane protein without nucleic acid
PrP-BSE → induces a post-translational change in the protein
Aggregation & accumulation in the brain →
Progressive neurologic dysfunction
B. S. E.
- incubation
- age of onset
-signs?
Long incubation period
Age of onset: 4 – 6 years (range 20 mo– 18 years)
Insidious onset
<><>
Signs:
Apprehensive; Fearful of handlers
Separate from herd; Excitable (extreme)
Hyperesthesia; Hyperresponsive
May be extreme!!
<><>
Pytalism
Increased head rubbing
Muscle fasciculation
Vocalization (excessive)
Head tossing
Excessive licking
Yawning
Head butting
Flehmen response
Restlessness
Relative bradycardia
Recumbency
B. S. E.
Infectivity; tissues affected
Brain
Spinal cord
Retinal tissue
Optic nerve
Nerve ganglia – cervical, thoracic, trigeminal
Facial, sciatic nerves
Distal ileum (GALT)
B. S. E.
- prevention considerations, control
- experimental infection species
- Likely lone entity; possible link to Scrapie ? ?
- Change in rendering processes resulted in spread.
- Animal byproducts fed to animals.
<><>
Ban feeding of bovine meat, bone products to
cattle.
People – new variant CJD
<><>
Experimental infection - other animals: mice,
sheep, goats, pigs, cats, mink, primates
BSE - Diagnosis, PM
No ante-mortem test available
<><>
Necropsy specimens:
Histology: neuronal degeneration, intraneuronal vacuolation
Preceded or concurrent with accumulation of PrP- BSE.
Obex of the medulla = tissue of choice
BSE – Differential Diagnosis
Viral encephalopathies:
Rabies
Pseudorabies
Borna disease
<><>
Listeriosis
Polioencephalomalacia
Lead poisoning
Parasite migration
Abscesses
Tumors
Vitamin A toxicity
Hepatoencephalopathy
Metabolic diseases
BSE
- tx, prognosis
- resistance? sensitivity?
Treatment: None
Prognosis: Grave
<><>
Organism resistant to:
- Autoclaving
- Disinfectants
- Rendering
- Long-term storage
- Ultraviolet radiation
- Thawing
- Boiling
- Formalin incubation
<><>
Organism sensitive to alkaline digestion
BSE – Control Canada
1997 – mammalian protein sources eliminated in bovine feeds (except swine, equine sources)
Some bovine tissues cannot enter human food chain: skull, brain, trigeminal ganglia, eyes, tonsils, spinal cord, dorsal root ganglia of cattle over thirty months of age, distal ileum
Note: material that cannot enter human food
chain cannot enter into animal feed, pet food,
fertilizer
Scrapie
- what is this?
- who does it affect
- agent
- vs BSE??
Transmissible spongiform encephalopathy
Sheep, goats
<><>
PrP-Sc
Distinct from BSE
Three different types
<><>
Sheep can be experimentally infected with BSE but not know to occur naturally
Scrapie
- age affected?
- progression
- signs
Age – usually 1-5 years of age
Slow onset/progression – over several months
Early behavioral changes, weight loss
> Separate from flock-mates
> Nervous, restless
Pruritus – scratch against objects, with horns & hooves
Scrapie
Pruritus consequences
- ddx??
Head, withers, flank, tail base, back, rump, lower limbs
Secondary wool loss, excoriation, dermatitis
May have ocular & aural lesions
<><>
“Scratch reflex” – nibbling, lip licking, rhythmic
head movements
Note: this response may occur w other neurologic or skin diseases (ectoparasites!!)
Scrapie
Other clinical signs (not pruritus)
Bruxism, pytalism, regurgitation
Tremors – head, body
Depressed demeanor
Exercise intolerance
Hypermetria
Ataxia
Stupor, collapse, convulsions
Death
Scrapie
Pathophysiology –
- tissue
- transmission
- timing of signs
Found in nervous tissue and GALT
<><>
Also can be found in:
Lymphoreticular tissue
Kidneys
Placenta
<><>
Transmission mostly during lambing season
(placenta and fluids)
<><>
Spread by way of the vagus nerve to the
brainstem brain
<><>
Neural dysfunction may precede histologic
changes or PrP-Sc accumulation
Scrapie
- Epidemiology, geography
- etiology
- resistance?
Occurs world wide, except Australia & New Zealand
Genetic basis to susceptibility & resistance
<><>
PrP gene:
3 important codons (171, 136, 154)
- Site 171 alleles:
QQ – susceptible
QR - resistant
RR – resistant
<><>
Resistance selection: pedigree, phenotypic
expression of disease, genetic testing for resistance