Farm Animal

Listeriosis

• gram +, facultative intracellular/anaerobic bacteria seen in environment & poorly ensiled feeds, often causes sporadic Dz

• infection of brainstem via hematogenous spread or via CN

• clinical signs: fever, ear drooping, head tilt, facial deviation, exposure keratitis, anorexia/depression, inability to swallow, dehydration → systemic acidosis, bruxism, decreased rumination, asymmetric CNS signs, deficits to CN V, VII, VIII

• Dx: IHC, rule out middle/inner ear infection

Polioencephalomalacia

• glycolysis inhibitors (ex: thiaminases) → reduced/absent ATP production

• causes: thiamine deficiency, thiaminases, rumen acidosis/dysbiosis, lead poisoning, salt toxicity, sulfur toxicity

• causes brain swelling inside calvarium → increased pressure, edema, & necrosis

• clinical signs: separate from herd, not eating/drinking, walking into things, star gazing, abnormal gait, recumbence/paddling

• Dx: at necropsy - grey matter necrosis w/flat gyri ± cerebellar or occipital herniation, bright green under UV

Meningitis

• inflammation of meninges + brain common in young animals due to FPT

• clinical signs: fever, depressed/lethargic, abnormal mentation, inability to nurse, head/neck extended (opisthotonus/star-gazing), hypopyon (fibrin + WBC in anterior chamber)

Parasitic encephalitis

• caused by Parelaphostrongylus tenuis, deer definitive host, ruminants aberrant host, common in camelids

• ruminants ingest encysted larva → migration from GI to spinal canal → inflammatory response

• clinical signs: dysfunction of rear limbs (wide base, short strided gait, dragging feet) ± forelimb weakness

  • pts alert + responsive

• Dx: CSF (eosinophils)

Most common CNS disorders in farm animal

• encephalitic listeriosis

• polioencephalomalacia (cerebrocortical necrosis)

• aberrant migration of parasites

Large animal neuro exam

• thorough history - progressive or regressive?

• standard neuro exam

• lesion localization