Equine herpesviruses 1 (EHV-1) and 4 (EHV-4)--epidemiology, disease and immunoprophylaxis: a brief review.
Authors: Patel J R, Heldens J
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Equine Herpesviruses 1 and 4—Epidemiology, Disease and Immunoprophylaxis EHV-1 and EHV-4 present distinct clinical challenges in equine populations, with both causing febrile respiratory disease but EHV-1 uniquely responsible for the more serious complications of abortion, paresis and neonatal foal mortality. The pathological mechanism underpinning these severe manifestations involves necrotising vasculitis and thrombosis arising from direct viral lytic infection of capillary endothelial cells, typically initiated by reactivation of latent EHV-1 harboured within leukocytes—though the precise host factors triggering such reactivation remain incompletely characterised. Despite five decades of vaccine development using both conventional and contemporary immunological strategies, progress has lagged considerably behind what has been achieved with related alpha-herpesviruses in cattle and pig populations. Emerging evidence surrounding temperature-sensitive live EHV-1 vaccine candidates demonstrates encouraging efficacy, potentially offering the field more effective immunoprophylactic options going forward. For practitioners involved in herd health planning and neonatal foal management, understanding that EHV-1 reactivation rather than primary infection often drives the most catastrophic outcomes underscores the importance of stress minimisation and rigorous biosecurity protocols in breeding establishments.
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Practical Takeaways
- •Recognize EHV-1 as the primary viral threat for reproductive loss and neurological disease in horses; monitor pregnant mares and young foals closely during outbreak situations
- •Understand that latency and unpredictable reactivation complicate control strategies; implement biosecurity measures and consider vaccination protocols appropriate to your operation's risk profile
- •Stay informed about emerging vaccine options, particularly temperature-sensitive live vaccines, which may offer improved protection compared to conventional inactivated vaccines
Key Findings
- •EHV-1 is the primary cause of abortions, paresis, and neonatal foal deaths in horses, with the central pathology being necrotising vasculitis and thrombosis from endothelial cell lytic infection
- •Reactivated EHV-1 from latently infected leukocytes likely initiates vascular lesions, though host factors governing reactivation remain poorly understood
- •Vaccine development progress against EHV-1 and EHV-4 has been slow compared to alpha herpesviruses affecting cattle and pigs despite over five decades of research
- •Live temperature-sensitive EHV-1 vaccine candidates show promising recent data for immunoprophylaxis