Ovine Neurology Flashcards
What are the 6 classifications of neurological disease by cause. Give an example for each.
- DEVELOPMENTAL eg Swayback, DandyWalker malformation - hydrocephalus, ’Daft Lamb’ cerebellar hypoplasia
- INFECTIOUS
–Bacterial eg meningitis, abscesses
–Viral eg. Border disease
–Parasitic eg. Gid
- METABOLIC/NUTRITIONAL – eg CCN
- TOXIC eg. Lead poisoning
- INJURY eg. cervical subluxation (rams)
- PERIPHERAL NERVE eg. Radial (kangaroo gait) or sciatic damage
Name the 2 most common neuro diseases in sheeps
Pregnancy Toxaemia
Hypocalcaemia
What type of disease is scrapie?
Transmissable encephalopathy
What is the main source of infection of scrapie?
Placenta in lambing
What is scrapie caused by?
An accumulation of an altered host protein – protease-resistant prion
Name Clinical signs of scrapie?
- Paresis and ataxia, especially hindlimbs
- Quadriplegia and recumbency
- Separation from the rest of the flock
- Depression, anxiety or hyperexcitability
- Head tremor & low head carriage
- Pruritus (“nibble” response)
- Weight loss, bruxism, cud-dropping
- No menace response
- Usually sheep above 2 years old
How do we diagnose scrapie?
Detection of the PrPsc in brain on post-mortem
Isolation of PrPsc in biopsy of lymphoid tissue (tonsillar tissue or rectal mucosa)
Why is scrapie rare?
Testing and eradication programme! So has gone from very common to rare. Slecting and extinguishing VRQ and HRQ genotype
Which scrapie is still seen?
Atypical
What are clinical signs of maedi visna?
Visna virus (also known as visna-maedi virus, maedi-visna virus and ovine lentivirus) from the genus Lentivirus and subfamily Orthoretrovirinae, is a “prototype”retrovirus that causes encephalitis and chronic pneumonitis in sheep.
- The sheep may be ataxic, paretic and drag a leg. Hind legs are often affected more than the front but all 4 can be involved.
- They may also have depression, head tilt and fine tremor of the lips. Occasionally they may also appear to be blind.
Name 2 differentital for maedi visna (3) How do you distinguish?
Listeriosis, aberrant larval migration, spinal abscess/mass and scrapie, and so a diagnostic PM should be performed
What is the neuro component of maedi visna accompanied by?
Cachexia (no appetite) and chronic wasting.
What are the 2 forms of swayback?
- Congenital
- Delayed
What is congenital swayback caused by?
•Copper deficiency little extra feed in mid-late pregnant hill ewes (susceptible breeds and on deficient pasture)
What is seen in sheep with swayback?
- Lots of stillbirth, small weak lambs with fine head tremors.
- Lambs bright but weak on hind legs ->stumbling/swaying gait. Fine boned & dull coats.
How can we diagnose congenital swayback?
Diagnosis - do histopath on brain & spinal cord.
When is delayed swyback seen and what is the cause?
Normal at birth but progressive weakness of pelvic limbs at 2-4 month old
Demyelination & reduced myelin synthesis in spinal cord. So only becomes apparent when the lamb grows
How can we prevent delayed swayback?
Inject chelated copper or CuO needle or give glass bolus in mid pregnancy BUT NOT to Texel or other continental breeds and primitive native breeds as highly susceptible to copper toxicity
What is acute coenurosis and what is seen?
Seen 10 days after turning onto land HEAVILY contaminated with dog faeces. Pyrexia, listlessness & head aversion. Death 4-5 days after neurological signs.
What is chronic coenurosis and what is seen?
Much more common in growing sheep 6-18 mths. V rare >3yrs old.
Insidious onset with slowly progressive focal lesion.
2-6mths from Larval hatching to migration & onset of neurological dysfunction
What is the larval stage of Taenia multiceps?
Coenuris cerebralis
How does Coenuris cerebralis complete its cycle?
LC completes when the definitive host (dog) ingests sheep brain (see it more in highlands as don’t have complete clearance of fallen stock)
Name Clinical signs of coenurosis if it is in the cerebral cortex?
Name clinical signs of coenurosis in the vestibular?
Head tilt towards affected side