11/20/2025
Joni Morrison
What is Equine Herpesvirus (EHV)?
You've probably heard it called Rhinopneumonitis, a respiratory tract disease that results in "snotty noses," but EHV is more than that. Depending on the strain, this virus can also cause abortion in broodmares, and equine herpesvirus myeloencephalopathy (EHM) — the often-deadly neurologic form of the disease.
Because EHV is endemic in many equine populations, most mature horses have developed some immunity through repeated natural infection. However, they remain a source of infection for other susceptible horses, like weaned foals and yearlings, who usually display symptoms of the respiratory form of the disease in autumn and winter. Performance and show horses are also more vulnerable to the disease, as they commingle with unfamiliar equines in close quarters while under stress from travel and competition.
Proper biosecurity protocols can help reduce EHV outbreaks and other disease transmission. A variety of vaccines are also available for protection against both the respiratory and abortive form of the disease, but there is no equine licensed vaccine at this time that has a label claim for protection against the neurologic form (EHM).
Consult your primary equine veterinarian to learn more about this disease and work with them to determine the optimal vaccine protocol for your horses.
You can learn more about all three forms on the Equine Disease Communication Center's website here: https://equinediseasecc.org/infectious-diseases
