22.5.4: Neurological conditions of ruminants Flashcards
Metabolic diseases of ruminants producing neurological signs
- Pregnancy toxaemia
- Nervous ketosis
- Cerebrocortical necrosis (CCN)
- Swayback
- Hypovitaminosis A
- Hypomagnesaemia
Clinical signs of pregnancy toxaemia (early stages)
- Separation from group
- Apparent blindness - seems alert but does not want to move even if dog present
- Bump into obstacles
- Head-pressing
Clinical signs of pregnancy toxaemia (later stages)
- Marked drowsiness
- Facial twitching, jaw champing, salivation
- Deviations of head position
- Star-gazing and ataxia
- Seizures -> marked drowsiness seen between seizures
- Ketone breath
Clinical signs of pregnancy toxaemia (final stages)
- Recumbency (this occurs after 3-4 days)
- Comatose state lasting 3-4 days
- If foetal death occurs, ewe appears to recover but secodary toxaemia results in deterioration and death
If a ewe with pregnancy toxaemia appears to start to recover (without any treatment being administered) what might you be suspicious of?
- Suspicious that foetus(es) have died
- Need to take care that toxaemia does not end up killing the ewe
Treatment of pregnancy toxaemia
- Parenteral glucose - start with this to stop the animal dying😀 e.g. 5-7g glucose IV, may need to repeat 6-8x daily
- IV fluids: Hartmann’s saline
- Oral propylene glycol - 100ml daily. In milder cases, this alone may be effective.
- Consider inducing if in early stages of disease; if you do not think ewe will survive between induction and parturition, consider C-section🔪
- Consider eye lube - can’t blink so may get exposure keratitis
- Consider implications and management for rest of the flock
Prevention and control of pregnancy toxaemia
- When clinical cases occur, monitor rest of flock and treat affected animal immediately - prognosis is poor especially once recumbent
- Ensure there is a rising plane of nutrition in the second half of pregnancy; if need be restrict feed in early pregnancy to allow this
- Recommend scanning and feeding singles/twins/triplets separately if possible
Describe the aetiology of nervous ketosis
- Uncommon presentation of ketosis
- Likely due to isopropanolol (the breakdown product of acetone)
- Hypoglycaemia likely to contribute
- Ketone bodies further exacerbate signs
True/false: nervous ketosis cows, although displaying abnormal mentation, are usually placid.
False
They are dangerous and will only stop when they walk into something that doesn’t move.
Take care around these cows.
Clinical signs of nervous ketosis AND what differential should also be on your list when you see these
Sudden onset neurological signs in short recurring bouts
* Circling and aimless wandering
* Crossing limbs and ataxia
* Apparent blindness, walking into objects, head-pressing
* Hyperaesthesia
* Mild tremors
Key differential: ⚠️BSE⚠️
Diagnosis of nervous ketosis
- Clinical signs
+ - BHB concentration >3.0 mmol/L
Treatment of nervous ketosis
- 💉IV glucose (500ml of 50% solution) -> will produce a rapid improvement but this is transient and will only last 3-4hrs
- Oral propylene glycol - 300ml once daily for 5 days
- Glucocorticoids - limited evidence base, may be justifiable in v sick cases. Thought to help due to glucose repartitioning.
What is another name for cerebrocortical necrosis (CCN)?
Polioencephalomalacia
Aetiology of CCN
There is a deficiency in thiamine (Vitamin B)
* High concentration of thiaminases are formed in the rumen (we don’t know why this happens) -> these destroy the thiamine produced by microbes
* Thiamine is an important component of metabolic enzymes. Without it, there is increased pyruvate.
* This has a negative effect on glucose pathways -> damage to cerebral neurones.
What is sulphur-induced CCN and which animals is it most commonly seen in?
- Seen in animals fed diets high in sulphates
- Young cattle on feedlots (6-18 months old)
Describe the typical presentation and clinical signs of CCN
- Usually seen in young, growing animals -> weaned lambs and calves most commonly
- There is typically a history of recent dietary change (about 2 weeks prior) -> this causes disruption of the rumen microflora
Clinical signs - this is a condition of the cerebrum so we see abnormalities of mentation:
* Sudden onset blindness
* Aimless wandering and circling
* Head pressing
* Star gazing
* Progress over 12-24hrs to lateral recumbency and opisthotonos
* Death in a few days if untreated
This lamb was weaned approx 2 weeks ago. Over the past 12hrs it has progressed from aimless wandering and circling to its current posture. What is your diagnosis and how will you treat the lamb?
This lamb has CCN
* Treat with Vitamin B1 given IV slowly (initial treatment)
* Then follow up with up to 5 doses every 3hrs (can be IV or IM)
You obtain the brain of a lamb that died after showing neurological signs. The brain fluoresces under UV light. What is your diagnosis?
CCN
You suspect CCN in a lamb. What else might be on your differential list?
- Meningitis
- Lead poisoning
- Vitamin A deficiency
How do you definitively diagnose CCN ante-mortem?
You can’t however history + clinical signs + response to treatment are highly suggestive.
* To definitively diagnose, need PM -> brain fluoresces under UV light
True/false: sulphur-induced CCN will response to thiamine given as treatment.
False
It will not respond
Treatment and control of CCN
- Thiamine (Vitamin B1) 10mg/kg given slowly IV
- Then repeat every 3hrs up to 5 doses - can give IV or IM
- Use B1 products - often multivitamins will not have high enough B1 needed; if you only have multivitamins available, use a high volume of them
- Supportive care: may need dexamethasone 1mg/kg if cerebral oedema
Ongoing management
* Supplementation of diet with thiamine for ongoing control (3 mg/kg dry matter - may need higher on some farms) - cases tend to be sporadic on farm so may not need to do this
* Ensure adequate roughage in diet
* Ensure sulphur in diet is appropriate
A ruminant is presenting with neurological signs. You are concerned about CCN and meningitis. Do you:
a) PM the ruminant and send for post-mortem so that you can ascertain the cause and implement herd-wide measures
b) Take a CSF sample to rule out meningitis
c) Take a blood sample to assess Vitamin B1 levels and diagnose CCN if present
d) Treat for both meningitis and CCN
a) PM the ruminant and send for post-mortem so that you can ascertain the cause and implement herd-wide measures
b) Take a CSF sample to rule out meningitis
c) Take a blood sample to assess Vitamin B1 levels and diagnose CCN if present - no, you cannot diagnose CCN this way!
d) Treat for both meningitis and CCN - this is cheap and effective - consider stewardship implications and choose an appropriate antibiotic if you are going to do this
Which species can be affected by swayback and what causes it?
Swayback = copper deficiency of dams during mid-pregnancy.
Sheep and goats can be affected.