Sheep CNS Diseases Flashcards
In sheep, what other disease types can neuro disease be confused with?
- What is important in order to combat this confusion?
Locomotor.
General weakness.
Depression (e.g. metabolic disease).
Weakness e.g. from starvation, from anaemia etc.
- A good hx and CE.
Basic clinical reasoning and logical approach to a neuro case?
Hx.
CE.
Problem list.
Differential list.
Dx tests.
Dx.
Tx.
Prevention.
Hx taking in ovine neuro cases?
Number of animals affected.
Congenital or acquired?
Age.
Progressive?
Diet.
Management.
Pregnancy status.
Response to treatments so far.
CE of neuro sheep.
Observe group/individual undisturbed.
Look for unusual behaviour.
- social/grazing – isolating self?
- Irritable – response to flies, other sheep, humans?
- Stance – wide-based to keep balance.
Locomotion – ataxia or collapse on running.
Head tilt / circling / head pressing?
Recumbency.
Carry out full CE.
- look for normal TPR of sheep:
– HR = 70 - 80
RR = 16 - 35
T = 38.3 – 39.9 ֯ C
Rumen turnover = 1 – 2 per minute
Sheep neuro exam.
Same approach for cattle and other animals.
- except for needing handler to restrain.
Test cranial nerve function.
And peripheral nerve function.
Neurolocalisation areas?
Cerebrum.
Cerebellum.
Brainstem and cranial nerves.
Spinal cord and peripheral nerves.
Common neuro diseases in adult sheep and the locations of these?
Cerebral:
- CCN.
- Bacterial meningitis.
- Pregnancy toxaemia.
- Hypocalcaemia.
- Hypomagnesaemia.
- Cerebral abscess.
- Coenurosis.
Cerebellar:
- Scrapie.
Brainstem:
- Listeriosis.
Peripheral nerves:
- Louping ill.
- Ryegrass staggers.
CCN…(aka…)
Epidemiology.
Hx/signalment.
Cerebrocortical necrosis aka Polioencephalomalacia.
Epidemiology:
- thiamine (vit B1) deficiency.
- change in diet leads to excess thiaminase producing microbes, leads to altered glucose metabolism, leads to damage of the superficial brain tissue.
– clinical signs arise ~1-2w later.
Hx/signalment:
- lambs older than 12w, adults.
- more common in animals fed cereal diet.
- seen after dietary change.
- disease progresses over 3-5d.
CCN clinical signs.
Differentials.
Dull.
Wander aimlessly.
Appear bling.
Ataxic and staggering gait.
Recumbent w/ opisthotonus.
Ddx depends on age.
- sulphur toxicity.
– will not respond to tx.
- brain abscesses.
- meningitis.
- listeriosis.
- visna.
- louping ill.
Dx of CCN.
PM.
- histopathology of brain.
- fluoresce under UV light.
Tx of CCN.
Vitamin B1 10mg/kg IV (high dose).
Then 5-10mg/kg IM q3hrs.
Tx for 3d.
Response to tx confirms dx and is good if treated early.
Coenurosis (Gid).
Not common generally.
Seen in areas where sheep carcases are not disposed of correctly.
Life cycle of coenurosis cerebralis in sheep and dog?
Sheep eats grass contaminated by tapeworm segments in dog faeces > tapeworm embryos grow into cysts in sheep brain and spinal cord > sheep becomes ill w/ coenurosis cerebralis, gets thin and dies > dog eats infected brain and spina; cord from dead sheep > tapeworm develops in dog gut > tapeworm segments in dog stools on grass > and so cycle restarts.
Clinical signs of coenurosis (gid) in sheep?
Ddx for gid/coenurosis?
Chronic, progressive disease w/ weight loss.
CNS signs variable depending on location of cysts, usually unilateral.
- cerebrum – blindness contralateral to cyst.
– proprioceptive deficits in contralateral limbs.
– circling.
– frontal –> head-pressing.
Progression slow.
Animals appear “giddy”.
Skull over the cyst may be soft.
Ddx = listeriosis, CCN, Visna, Louping Ill, brain abscess.
Dx of Gid/Coenurosis.
Hx e.g. farm dogs not treated for tapeworm, inappropriate carcass disposal.
Clinical signs.
PM - hydatic cyst found in the brain.
Tx of Gid/Coenurosis?
Sx removal of the cyst - good chance of survival.
Euthanasia.
Prevention of Gid/Coenurosis?
Education of farmers and dog owners.
Regular tx of dogs to kill tapeworms (Praziquantel).
Dispose of sheep carcases.
Avoid grazing sheep on ground recently used by hounds or for sheep trials.
Do not feed uncooked sheep heads to dogs.
Scrapie…
1. Classical.
2. Atypical.
Transmissible Spongiform Encephalopathy. NOTIFIABLE!
1. Animals aged between 2 and 5yrs.
Highly contagious.
Spread via colostrum and milk.
Areas contaminated w/ birth fluids/placenta etc.
2. Animals usually over 5yrs.
Usually seen in individual animals (probably not contagious).
- Clinical signs of classical scrapie?
- Clinical signs of atypical scrapie?
- Should be suspected if 2 or more of the following:
- abnormal behaviour.
- absent menace response.
- positive scratch test or alopecia / skin damage.
- inco-ordination.
- tremor. - Should be suspected if animal over 5yrs and 2 or more of the following:
- abnormal behaviour.
- absent menace response.
- compulsive circling or circling blindfolded.
- incoordination.
- tremor.
- loss of BC.
- Dx of Scrapie?
- Scrapie prevention and control.
- If suspected, call APHA and stop any movement.
PME - brain histopathology. - Compulsory Scrapie Flock Scheme.
- if case confirmed.
– cull all small ruminants on holding.
…or…
– genotype all and cull all susceptible plus goats.
National Scrapie Plan (2001).
- surveillance.
- random testing of fallen stock.
- testing of sheep over 18m old slaughtered for human consumption.
Listeriosis.
Gram +ve anaerobe Listeria monocytogenes.
Survives on pasture, in food, silage.
Associated w/ less acidic pH of spoiled silage (pH <5.00) enhances multiplication of Listeria monocytogenes.
Tend to see in winter when animals are housed and fed supplementary silage.
What neurological disease does listeriosis cause?
- clinical signs of this?
Meningoencephalitis.
- dull.
- pyrexic.
- drool saliva.
- facial paralysis.
- circling.
- head tilt.
- collapse.
- depression.
- death (w/in 10-14d).
Non-neuro signs of listeriosis.
- abortion, septicaemia, diarrhoea.
Dx of listeriosis.
Hx and clinical signs.
Test CSF - lymphocytosis, monocytosis, organisms, but may be normal CSF.
Run blood haematology.
- neutrophilia (not definitive).
Tx of listeriosis?
Recovery rate of listeriosis?
ABX suitable for Gram +ve bacteria.
- and able to cross CSF.
So, high dose penicillin IM or IV depending on formulation.
- BID for 5d.
Husbandry:
- nursing, fluids, nutrition, warmth.
Recovery rate = 30%.
Long recovery period.
