🩺 Vet’s 2025 Guide to Equine Viral Hepatitis

By Dr Duncan Houston BVSc

1. What Is Equine Viral Hepatitis?

Equine viral hepatitis refers to inflammation and liver injury caused by viral infections—primarily Equine Parvovirus‑Hepatitis (EqPV‑H) leading to acute Theiler’s disease, and Equine Hepacivirus (EqHV) associated with chronic, often subclinical liver inflammation :contentReference[oaicite:3]{index=3}.

2. Pathogens & Transmission

• EqPV‑H: Parvovirus linked to fatal acute hepatitis after blood-derived products; prevalent on affected farms (up to 79 %) :contentReference[oaicite:4]{index=4}. Experimentally induces hepatitis with increased liver enzymes around 5 weeks post-infection :contentReference[oaicite:5]{index=5}.
• EqHV: A hepacivirus flavivirus; about 40 % of US horses show infection but only ~20 % become persistently affected, often without clinical signs :contentReference[oaicite:6]{index=6}.
• Also, rare pegiviruses (including Theiler’s disease–associated virus) may contribute :contentReference[oaicite:7]{index=7}.

3. Clinical Signs

• Acute EqPV‑H / Theiler’s disease: Sudden lethargy, inappetence, jaundice, discolored urine, fever, colic, photosensitization, and neurological signs like ataxia or head-pressing :contentReference[oaicite:8]{index=8}.
• Subclinical EqPV‑H/EqHV: Often silent; mild enzyme elevations may be the only clue :contentReference[oaicite:9]{index=9}.
• Chronic EqHV: Persistent infection may cause gradual liver enzyme elevations and vague signs like lethargy or poor performance :contentReference[oaicite:10]{index=10}.

4. Diagnostic Approach

• Clinical signs and serum chemistry: elevated AST, GGT, GLDH, bile acids, bilirubin :contentReference[oaicite:11]{index=11}.
• \ PCR for EqPV‑H/EqHV on blood or frozen serum—collect at first visit and repeat for persistence :contentReference[oaicite:12]{index=12}.
• Liver biopsy and histopathology may confirm disease severity :contentReference[oaicite:13]{index=13}.
• Rule out non-viral causes: toxins, bacterial infections, metabolic/endocrine disease :contentReference[oaicite:14]{index=14}.

5. Treatment & Supportive Care

There is no direct antiviral therapy. Treatment focuses on:

• IV fluids (including dextrose), nutritional support, anti-inflammatories (e.g., flunixin/Banamine), antibiotics if bacterial involvement suspected :contentReference[oaicite:15]{index=15}.
• Care for hepatic encephalopathy: lactulose, antimicrobials (like metronidazole), and a calm environment to prevent neurologic deterioration :contentReference[oaicite:16]{index=16}.
• Antioxidants (vitamins E/C, SAMe) may support liver cell recovery :contentReference[oaicite:17]{index=17}.
• Pain management with low-dose NSAIDs; minimize risk to gastrointestinal and renal health.
• Continuous monitoring of vitals, liver enzymes, clotting factors, and neurologic signs.

6. Prognosis

• EqPV‑H peaks in severity; survivors often clear virus within weeks and may fully recover—but severe acute cases carry high mortality :contentReference[oaicite:18]{index=18}.
• EqHV has a good prognosis—persistent infection may not impact health unless clinical signs appear :contentReference[oaicite:19]{index=19}.
• Mild/moderate hepatitis often resolves with supportive care; chronic fibrosis may impair long-term liver function :contentReference[oaicite:20]{index=20}.

7. Prevention Strategies

• Avoid equine blood products unless screened; observe response period (~4–10 weeks) :contentReference[oaicite:21]{index=21}.
• Screen biologics for EqPV‑H and EqHV using PCR.
• Practice hygiene and management to prevent iatrogenic or horizontal transmission :contentReference[oaicite:22]{index=22}.
• Annual hepatic health check: liver enzymes, bile acids, and PCR if indicated.
• Implement biosecurity: isolate symptomatic horses, disinfect equipment, quarantine new arrivals.

8. Monitoring & Follow‑Up

• Track clinical progress and lab values weekly during acute care, then monthly.
• Repeat PCR in 4–8 weeks to confirm viral clearance.
• Perform hepatic ultrasound/biopsy for persistent enzyme elevations.

9. Ask A Vet Support 🩺

With Ask A Vet you can:

• Share lab results and serum PCR outcomes for expert interpretation.
• Receive guidance on fluid therapy, lactulose dosing, and antioxidant use.
• Get support monitoring neurologic signs and hepatic encephalopathy management.
• Access biosecurity checklists and vaccination screening protocols.
• Schedule follow-up plans and individualized recovery timelines.

Download the Ask A Vet app now for expert liver-health support and peace-of-mind in 2025 and beyond! ❤️

10. Quick Reference Table

11. Final Thoughts

Equine viral hepatitis—from acute EqPV‑H to chronic EqHV—requires vigilance, early detection, and supportive management. With proper diagnostics, liver support, and preventive measures, most horses recover well. Ask A Vet brings clarity and continuity to every step—from identifying signs to ensuring full recovery—helping you protect your horse’s liver health in 2025 and beyond. ❤️