Equine Herpesvirus (commonly called EHV) is one of the most important infectious diseases affecting horses of all breeds and disciplines. While many horse owners have heard of EHV, understanding how it spreads, how to recognize early signs, and how to prevent outbreaks can make all the difference in protecting your herd’s health and minimizing disruptions to training, breeding, and competition schedules.

What Is Equine Herpesvirus?

Microscopic View of Virus Cells such as EHV

Equine Herpesvirus (EHV) is a common and highly contagious virus that affects horses around the world. There are several types of EHV, but EHV-1 and EHV-4 are the ones that most often cause problems. Both can lead to respiratory illness, similar to a cold or flu in horses. EHV-1 can also be more serious, as it’s linked to pregnancy loss, illness in newborn foals, and a neurologic condition called equine herpesvirus myeloencephalopathy (EHM).

EHV does not affect people, but it can spread easily between horses. One of the biggest challenges is that some horses can carry the virus without looking sick at all. These horses may still spread EHV, especially during times of stress, travel, or heavy training, which can cause the virus to “wake up” and become active again.

How Does EHV Spread?

EHV is highly contagious among horses and spreads through:

  • Direct horse-to-horse contact (nose-to-nose or close proximity)
  • Aerosolized respiratory droplets (from coughing or sneezing)
  • Indirect contact via contaminated equipment, tack, buckets, trailers, or even human clothing and hands
  • Shared water and feed sources 

Because infected horses can shed virus before they look sick, outbreaks can trace back to events, shows, or barns where horses from many backgrounds mix. This is why veterinary professionals often recommend isolating newly arrived horses for observation before introducing them to a home herd.

Early Detection: Testing and Veterinary Diagnosis

If you suspect EHV exposure or see clinical signs, contacting a veterinarian quickly is critical. Diagnostic testing typically includes:

  • Nasal swabs to check for viral DNA
  • Blood samples to evaluate immune response and viral presence
  • PCR testing, which is highly accurate for detecting active infection

Testing doesn’t just confirm whether a horse has EHV—it also helps determine which form of the virus is involved, including whether it’s the more serious neurologic type (EHM). Promptly involving your veterinarian is essential to help guide proper care, monitoring, and isolation steps, which can limit the spread of disease and support better outcomes.

Prevention: Biosecurity, Vaccination, and Management

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While no vaccine completely prevents EHV infection (especially the neurologic form), strategic use of vaccinations can reduce the severity and duration of respiratory and reproductive disease. Discuss with your veterinarian what vaccine schedule fits your horses’ age, health status, and travel plans.

Biosecurity is your strongest prevention tool:

  • Limit contact between your horse and those from other farms (such as while at shows)
  • Avoid horse movement to and from areas with known cases
  • Disinfect equipment, stalls, tack, and trailers regularly
  • Wash hands between handling different horses
  • Monitor temperatures daily during travel or after events

Keeping stress low (such as through proper nutrition, turnout, and careful handling) also supports immune function and reduces the risk of viral reactivation in carrier horses. Discover more of our top tips for supporting your horse’s immune system.

Responding to Possible Exposure

If EHV is confirmed or suspected on your property:

  1. Isolate affected horses immediately.
  2. Increase monitoring of all other horses (temps twice daily).
  3. Restrict movement on and off the farm.
  4. Notify your veterinarian and follow their guidance on testing and supportive care.

How Can I Keep My Horse Safe From EHV?

Equine Herpesvirus isn’t new, but its impact on horses and operations can be minimized with vigilance, good management, and strong biosecurity practices. With your veterinarian’s guidance, FarmVet is here to help keep your vaccination, biosecurity, and immune support needs fulfilled.