Equine Infectious Abortion Study Guide

Overview and Clinical Importance

Infectious abortion represents a significant cause of reproductive loss in mares with major economic implications for the equine breeding industry. The primary infectious agents include Equine Herpesvirus-1 (EHV-1), Equine Viral Arteritis (EVA), Leptospira spp., and various bacterial agents causing placentitis. Studies indicate that up to 40% of mares may experience pregnancy failure from fertilization to parturition.

Equine Herpesvirus-1 (EHV-1) Abortion

Equine herpesvirus-1 (EHV-1) is the most important viral cause of abortion in horses worldwide. It is a double-stranded DNA virus belonging to the Alphaherpesvirinae subfamily that establishes lifelong latency in up to 70% of infected horses.

Etiology and Epidemiology

EHV-1 and EHV-4 are ubiquitous pathogens. While EHV-4 primarily causes respiratory disease, EHV-1 causes respiratory disease, abortion, neonatal foal death, and equine herpesvirus myeloencephalopathy (EHM). Transmission occurs via direct contact with nasal secretions, reproductive tract discharge, aborted fetus, or placenta.