Horses worldwide face a serious threat from equine herpesvirus (EHV), a common cause of equine respiratory disease. In fact, research indicates horses are three times more likely to get rhinopneumonitis caused by EHV than flu caused by equine influenza virus (EIV). To combat this serious threat, a proper vaccination plan is key.

EHV infections often occur in autumn and winter in weaned foals and yearlings. Meanwhile, older horses are more likely to transmit the virus without showing signs of infection. The damage from infection can be devastating.

The most common types are equine herpesvirus type 1 (EHV-1), which can cause abortions, respiratory disease, and neurologic disease, and equine herpesvirus type 4 (EHV-4), which usually causes only respiratory disease, but can occasionally cause abortion. EHV-1 and EHV-4 infect the respiratory tract and can spread via aerosolized secretions from infected coughing horses, as well as direct or indirect contact with nasal secretions.

Clinical signs of the disease include fever, lethargy, anorexia, nasal discharge, and cough. Although EHV-1 can cause abortion outbreaks, EHV-4 has been associated with only isolated occurrences and is not a risk for contagious abortions