Equine Herpesvirus (EHV) Vet Guide 2025 – Dr Duncan Houston 🐴🧬

By Dr Duncan Houston, BVSc – expert guidance on equine herpesvirus infections, including respiratory, neurologic, reproductive, and pulmonary forms.

Introduction

Equine herpesviruses are pervasive in horse populations worldwide, with EHV‑1 and EHV‑4 being most clinically relevant. They can cause respiratory illness, abortion, neurological disease (EHM), coital exanthema (EHV‑3), and even pulmonary fibrosis (EHV‑5). This 2025 guide provides a comprehensive breakdown: forms, symptoms, diagnosis, management, prevention, and biosecurity strategies. 🧠

🧬 Forms & Transmission

• EHV‑1: Causes respiratory disease, abortion, neurologic EHM :contentReference[oaicite:3]{index=3}
• EHV‑4: Primarily respiratory in young horses :contentReference[oaicite:4]{index=4}
• EHV‑3: Causes coital exanthema—genital lesions :contentReference[oaicite:5]{index=5}
• EHV‑5: Linked to multinodular pulmonary fibrosis in adults :contentReference[oaicite:6]{index=6}

Transmission occurs via respiratory droplets, direct contact, fomites, aborted tissues, and reactivation from latent carriers :contentReference[oaicite:7]{index=7}.

⚠️ Clinical Signs & Syndromes

Respiratory (EHV‑1, EHV‑4):

• Fever (102–107 °F), nasal discharge, cough, pharyngitis, inappetence :contentReference[oaicite:8]{index=8}
• Lethargy, swollen lymph nodes, occasional conjunctivitis :contentReference[oaicite:9]{index=9}

Abortion (EHV‑1):

Mares may abort 2–12 weeks after infection, often showing little warning :contentReference[oaicite:10]{index=10}.

Neurologic (EHM, EHV‑1):

• Ataxia, hindlimb weakness, incoordination, tail/urine loss, recumbency :contentReference[oaicite:11]{index=11}
• Incubation: 4–10 days (up to 14); biphasic fever pattern :contentReference[oaicite:12]{index=12}

Coital Exanthema (EHV‑3):

Pustules or ulcers on genitalia, may spread to lips/teats, decreased libido, resolves in ~2 weeks :contentReference[oaicite:13]{index=13}.

Pulmonary Fibrosis (EHV‑5):

Chronic weight loss, respiratory distress, fever in mature horses :contentReference[oaicite:14]{index=14}.

🔍 Diagnostics

• PCR: Nasal swabs, blood for EHV‑1/4, late‑stage CSF in neurologic cases :contentReference[oaicite:15]{index=15}
• Virus isolation: From fetal/placental tissues in abortion cases :contentReference[oaicite:16]{index=16}
• Serology: Limited—cross‑reactivity; serum neutralization suggests exposure :contentReference[oaicite:17]{index=17}
• Neurologic diagnosis: PCR/CSF analysis and clinical signs :contentReference[oaicite:18]{index=18}

🩺 Treatment & Supportive Care

• NSAIDs and rest for fever and discomfort :contentReference[oaicite:19]{index=19}
• Antibiotics for secondary bacterial infections :contentReference[oaicite:20]{index=20}
• Acyclovir or valacyclovir in neurologic cases—efficacy still under study :contentReference[oaicite:21]{index=21}
• Heparin, steroids, antioxidants, supportive nursing in EHM :contentReference[oaicite:22]{index=22}
• Palliative care for EHV‑3: hygiene, isolation, sexual rest :contentReference[oaicite:23]{index=23}
• Supportive care in pulmonary fibrosis—no cure :contentReference[oaicite:24]{index=24}

🛡️ Prevention & Biosecurity

1. Vaccination: EHV‑1/4 vaccines—foal series then boosters every 6 months in high-risk :contentReference[oaicite:25]{index=25}
2. Isolation: New arrivals quarantined 21–28 days; infected horses kept 28 days after recovery :contentReference[oaicite:26]{index=26}
3. Hygiene: Disinfection, no shared buckets/tack, glove use for breeding :contentReference[oaicite:27]{index=27}
4. Stress reduction: Avoid transport, competition, handling during outbreaks :contentReference[oaicite:28]{index=28}
5. Pregnant mares separated from young horses during high-risk times :contentReference[oaicite:29]{index=29}

📊 Quick Comparison Overview

🌟 Final Thoughts & Ask A Vet Support

Equine herpesvirus poses serious health risks—from mild respiratory disease to life-threatening abortion and neurologic disease. Vigilant prevention through vaccination, strict biosecurity, early detection, and supportive care improves outcomes. In outbreaks, swift response with isolation and sanitation is key.

Need help managing vaccination protocols, outbreak planning, or patient care during EHV events? Ask A Vet delivers expert support, reminders, and tele-health consultations via our app. Download the Ask A Vet App now to protect your herd’s health and future. 📲🐎