11/20/2025
EHV outbreak facts and info:
Clinical signs include Fever with re**al temp of 102'F or higher, Nasal discharge, Lack of coordination, Weakness, Lethargy, Dribbling urine
Almost all horses have been exposed to EHV at some point.
A very small percentage of exposed horses get EHM, the neurological form. Horses can live but the prognosis is usually poor.
EHV incubation is 2-10 days.
Shedding is 7-10 days.
Transmission is nose to nose, 30 feet or less aerosol, contaminated hands/equipment/buckets
Quarantine is 21 days after exposure.
Is my horse exposed? If they were at an event with known cases, then yes.
If your horse WAS exposed do NOT vaccinate the horse, instead quarantine the horses for 21 days and monitor closely, especially re**al temp.
Recommendations for vaccinating horses:
Traveling horses: vaccinate with Calvenza (flu/rhino) if it has been more than 6 months since last vaccination.
Not traveling horses: if previously vaccinated, monitor closely. OR Vaccinate with Calvenza out of abundance of caution
Yearlings previously vaccinated: vaccinate with Calvenza now
Weanlings born to vaccinated mares over 5 months of age: Vaccinate now with Vetera Gold now and booster in 1 month.
Most importantly, let’s remember that horses travel all over the country all the time and are exposed to a lot of diseases. Biosecurity is important year round and every time we travel with our horses.
If you have specific questions, please reach out for more info!
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