🩺 Borna Disease in Horses: A Vet’s 2025 Guide | Dr Duncan Houston BVSc

Meta description: 🐎 A vet’s 2025 guide by Dr Duncan Houston on Borna disease in horses—signs, diagnosis, treatment, prognosis & herd management with Ask A Vet support.

1. 🧠 What is Borna Disease?

Borna disease is a rare but serious viral infection caused by Borna disease virus 1 and 2 (BoDV-1, BoDV-2), affecting the central nervous system of horses, sheep, goats, and occasionally humans. Transmission is believed to occur via infected small mammals (such as shrews and rodents) shedding virus in urine, saliva or feces. Once infected, the virus targets and inflames the brain and spinal cord causing behavioral and neurological signs.

2. 🌍 Where Is Borna Disease Found?

Borna disease has been diagnosed primarily in parts of Europe and Japan. Sporadic cases occur in endemic regions where reservoir species overlap with grazing areas. No confirmed natural human-to-horse transmission exists.

3. ⚠️ Why It Matters

Borna disease often begins subtly and progresses rapidly, making diagnosis challenging. Infected horses may experience severe neurologic dysfunction, and mortality can be high. Early recognition and supportive care are essential to improve chances of recovery.

4. 🧭 Recognizing Clinical Signs

Clinical signs of Borna disease are wide-ranging and may include:

• Behavioral changes: Exaggerated responses, anxiety, head-shaking, aggression or dullness
• Head-pressing / compulsive movements
• Ataxia & weakness: Stumbling, difficulty rising, swaying, or drifting
• Tremors or muscle fasciculations
• Seizures—in advanced disease
• Cranial nerve deficits: facial paralysis, eyelid droop, difficulty swallowing
• Hyperthermia or fever possible but non-specific

Onset may be subacute (days to weeks), often with fluctuating signs and periods of seeming improvement.

5. 🧪 How We Diagnose

• Thorough neurologic exam: gait evaluation, cranial nerve testing, menace and palpebral reflexes
• Blood tests: rule out infectious or metabolic causes; BoDV serology may indicate exposure but false positives exist
• Cerebrospinal fluid (CSF): collected via atlanto-occipital or lumbosacral tap—often shows increased protein, mild lymphocytic pleocytosis, and viral RNA via PCR
• MRI or CT scans: when available, may detect encephalitis lesions
• Postmortem confirmation: histopathology remains the definitive diagnosis

6. 🛠️ Treatment & Emergency Care

There is no specific antiviral treatment for equine Borna disease. Supportive therapy focuses on:

• Hospitalization & isolation: to provide care and minimize transmission risk
• Anti-inflammatory drugs: NSAIDs or corticosteroids to reduce brain inflammation
• Fluid therapy: IV fluids to maintain hydration and reduce metabolic effects
• Seizure control: benzodiazepines such as diazepam for seizure episodes
• Nutrition & feeding support: soft feed or tube feeding if neurological dysfunction impairs eating
• Monitor vitals and neurologic progression daily

7. 🩺 Prognosis & Outcomes

Prognosis is guarded to poor. Many affected horses deteriorate despite aggressive care. In less severe cases, some horses may slowly recover over weeks to months but often retain residual deficits. Euthanasia may be the compassionate decision if the horse remains severely recumbent, aggressive, or unable to safely eat or drink.

8. 🔍 Differential Diagnosis

Other conditions with similar neurologic signs include:

• Equine protozoal myeloencephalitis (EPM)
• Tetanus or botulism
• Wobbler’s syndrome (cervical vertebral malformation)
• West Nile virus encephalitis
• Equine herpesvirus myeloencephalopathy
• Lead toxicity, hepatic encephalopathy

These must be ruled out using targeted diagnostic testing.

9. 🛡️ Prevention Strategies

• Control rodent and shrew populations in and around stables and feed storage
• Maintain strict hygiene: clean water/feed and remove spilled grain
• Avoid storing bedding/feed in rodent-infested areas
• Monitor and isolate horses showing neurologic signs until diagnosis confirmed
• Consult local veterinary and wildlife authorities about disease prevalence

10. 🧭 Ask A Vet: Real-Time Vet Support

With **Ask A Vet**, you’re never alone when managing strange neurological signs in your horse:

• 📹 Send videos of unusual behaviors or gait abnormalities for early triage
• 📋 Receive urgent advice on CSF sampling, isolation, and fluid therapy
• 📆 Medication and recheck reminders—especially during extended monitoring
• 🎓 Attend webinars with Dr Duncan Houston on recognizing and managing neurologic disease

11. ❓ FAQs You May Have

Is Borna disease contagious to humans?

Transmission to humans is extremely rare. Standard biosecurity around handling neurological cases is sufficient.

Can a horse recover completely?

Complete recovery is uncommon. Mild cases may regain function, though subtle deficits often persist.

Are vaccines available?

No vaccines exist for equine Borna disease. Prevention relies on hygiene and environment control.

Should I euthanize immediately?

Decisions should follow veterinary assessment, severity of signs, and prognosis. Quality of life is the guiding principle.

12. ✅ Final Takeaway

• Borna disease is a rare, viral neurologic illness—early recognition matters
• Diagnosis relies on neurologic assessment and CSF testing (PCR)
• Treatment is supportive—anti-inflammatories, fluids, seizure control, feeding assistance
• Prognosis remains guarded; residual neurologic signs are common
• Isolation and stable hygiene minimize spread risk
• Ask A Vet provides expert guidance early and throughout a neurologic case 💙

🐾 Seeing Strange Behavior?

If your horse shows ataxia, head-pressing, aggression or tremors, send video or detailed history via Ask A Vet. I’ll help you triage, decide next steps, and coordinate diagnostics—giving you the expert support your horse needs. 🐎💞