Listeriosis is one of those “hear hoofbeats, think horse” neurologic problems in adult ruminants, especially in winter housing or silage-fed herds. Early recognition and therapy with strong supportive care greatly improve prognosis. Outcomes are worsened by treatment delays.
The Diagnostic Pattern
Listeriosis affects adult cattle, sheep, or goats that:
- Eat silage, especially spoiled or low-pH
- Stay indoors for the winter
- Show acute or subacute neurologic signs, usually unilateral cranial nerve deficits
These clusters are commonly seen in exam vignettes and real farm calls. If you recognize the patterns from a brief history (silage feeding + winter confinement + neuro signs), you’ve already identified the likely diagnosis.
The Classic Clinical Picture
Unilateral cranial nerve dysfunction with vestibular signs defines the disease. Look for:
- Head tilt and circling toward the lesion
- Facial asymmetry: unilateral droopy ear, ptosis, reduced menace and palpebral, and decreased facial sensation
- Depression, anorexia, drooling, +/- fever
- Ataxia and unilateral proprioceptive deficits
You’ll often notice a drooped ear and eyelid on one side. When you touch the affected side of the face, the animal will elicit less response due to decreased sensation.
Pragmatic, Timely Diagnosis
Use these practical, time-sensitive options to confirm your diagnosis:
- Base the clinical diagnosis on a compatible history (silage feeding) and neurologic exam findings (unilateral cranial nerve deficits + circling)
- CSF analysis may show a mononuclear pleocytosis and elevated protein
- Culture on tissue samples rarely yields positive results ante-mortem, but can ID bacteria using immunofluorescent techniques
- Rule out look-alikes, such as otitis, polio, lead toxicosis, and rabies using targeted history, physical exam, and herd context
Bottom line: start therapy as soon as the pattern fits. Don’t delay treatment (and risk worsening outcomes) waiting on sampling results.
Prompt Treatment
Begin antibiotics quickly and provide strong supportive care:
- Antibiotics: start penicillin or oxytetracycline immediately and continue for 1-2 weeks
- Supportive care: provide IV or oral fluids as indicated, ensure adequate nutrition, and manage bloat if present due to ruminal stasis, since untreated bloat can kill the animal
- Anti-inflammatories: use judiciously (clinicians continue to debate steroid use in neurologic listeriosis and exam writer won’t hinge a question on that controversy)
- Nursing care: keep animals on good footing, prevent recumbency complications, and monitor hydration and feed intake closely
Always review drug withdrawal times before committing a farm animal to an extended antimicrobial course and set client expectations early.
Prognosis & Client Communication
Prognosis ranges from guarded to poor and worsens with recumbency, severe neurologic deficits, or delayed treatment. Be transparent about:
- The likelihood of incomplete recovery, such as residual face paralysis or head tilt
- Treatment duration and cost, including residue constraints
- Herd-level implications: the appearance of one case signals an urgent need to evaluate silage quality
Prevention: The Silage Connection
Most cases can be prevented through strong forage management and feeding practices:
- Harvest, ferment, and store silage correctly, and discard spoiled or surface-contaminated material
- Feed silage in a way that minimizes aerobic spoilage
- Offer alternative forages if possible until silage can be confirmed “clean”
Recognize The Clues & Treat
The NAVLE® rewards clinicians who can recognize patterns early and act decisively. Adult ruminants in winter housing, silage exposure, and unilateral cranial nerve deficits should trigger immediate treatment, not diagnostic hesitation. Prompt antimicrobial therapy and aggressive supportive care offer the best chance for recovery, while delays quickly erode prognosis.
In practice and on boards, think listeriosis first, treat on suspicion, and communicate clearly with clients about realistic outcomes and prevention.
More from Zuku Learning:
- Master NAVLE® concepts
- Subscribe to the Question of the Day to receive a NAVLE® question delivered to your inbox daily
- Review the Ketosis in Fresh Dairy Cows: Causes, Diagnosis, and How to Treat It blog
- Review the Pregnancy Toxemia in Ewes & Does: Fast Field Diagnosis, Treatment, & Prevention blog
