Equine Alphaherpesvirus (Rhinopneumonitis) Vaccination Guidelines

Equine alphaherpesvirus type 1 (EHV-1) and equine alphaherpesvirus type 4 (EHV-4) infect the respiratory tract, the clinical outcome of which can vary in severity from subclinical to severe respiratory disease (rhinopneumonitis). Clinical infection is characterized by fever, lethargy, anorexia, nasal discharge, cough, and mandibular lymphadenopathy. Infection of the respiratory tract with EHV-1 and EHV-4 typically occurs in foals during the first weeks/months of life, and recurrent infections may occur in weanlings, yearlings, and young horses entering training, especially when horses from different sources are commingled. In addition to rhinopneumonitis, EHV-1 can also cause abortion, fatal neonatal disease, and neurologic disease (equine herpesvirus myeloencephalopathy; EHM).