Protozoal, Nutritional, & Toxic Neurological Diseases of Ruminants Flashcards
What is the most common protozoal cause of neurological disease in ruminants? What 3 signs are seen?
Coccidiosis
- seizures with opisthotonos and tonic-clonic movements
- medial strabismus
- eyelid snapping
(all with periods of normalcy!)
What risk factors are associated with nervous coccidiosis? How is it treated?
feedlot, winter
- Sulfonamides
- Amprolium
- TLC - protection during seizures
What is polioencephalomalacia?
blindness in young ruminants with thiamine deficiency (B1)
What is characteristic of polio in ruminants? What other signs are seen? What is not affected?
central blindness (+ PLR) with dorsomedial strabismus
- ataxia, tremor
- opisthotonos
- convulsions
- recumbency
rumen, no fever, normal CN
How is polio diagnosed? What is seen on necropsy?
- clinical signs and history
- response to thiamine (blindness may take a while to recover)
- CSF - mononuclear, mild protein elevation, xanthochromia
swollen, yellow cerebrum, autofluorescence of cortex under UV light
How is polio treated?
- thiamine (B1) - should have a response in 1-2 days
- control convulsions with Diazepam
- TLC
What ruminants are most commonly affected by polio? What is it most commonly secondary to?
younger —> 6-12 months
- ruminal acidosis (high sulfate diet) —> increases thiaminase production, which breaks down thiamine responsible for water balance in the brain
- competitive thiamine analogs - Amprolium overdose with treatment of Coccidiosis
How is polio prevented?
- supply moderate carbohydrate diet with increased roughage
- decrease sulfates in diet
- supplement diet with thiamine
excellent progosis when therapy is induced before incumbency —> neurologic changes may be permanent
What provides the most evidence for diagnosing polio?
necropsy
- swollen, slightly yellow cerebrum
- cerebellar and/or cerebral herniations (acute)
- autofluorescence of freshly cut surface of cerebral cortex under UV light (may not be present with acute death)
How can the rumen be used for diagnosing polio?
fluid evaluation —> sequela to grain overload, most common in calves on creep feeders —> rare for pH to be acidic, but the normal protozoal flora will not be present
What is the pathogenesis of polio?
BRAIN SWELLING
- gray matter necrosis due to lack of glycolysis with resulting brain edema and dysfunction of ATPase (Na, K) causes cellular swelling
- swelling causes pressure necrosis of the gray matter
- decreased thiamin limits transketolase activity
What is salt poisoning? What diagnostic history is associated?
overload of salt or lack of water intake results in hypernatremia with resultant neurological signs of cerebral edema —> aggressiveness, recumbency, coma
- distance to water
- frozen water source
- lack of water
How is salt poisoning diagnosed?
- serum and CSF Na markedly increased (>160 mEq/L)
- brain edema and cerebrocortical necrosis on histopath
(more common in pigs)
What is characteristic of vitamin A deficiency in cattle? When is this most common?
irreversible central blindness
when stock do not have access to succulent plants
What are the most common signs of lead poisoning?
- aggression, convulsions
- central blindness
- wandering, head pressing
- opisthotonos, odontoprisis
- bellowing
- eventual death