EHV-1 in Horses: What Every Caregiver Needs to Know to Protect Their Barn
When it comes to equine health emergencies, equine herpesvirus-1 (EHV-1) is one of the most serious threats horse caregivers can face. Highly contagious and sometimes fatal, EHV-1 spreads quickly and often silently—making fast action, strict biosecurity, and early veterinary involvement absolutely critical.
Whether you manage a boarding barn, care for a backyard horse, or oversee a competition stable, understanding how EHV-1 spreads and how to respond can make the difference between a single case and a devastating outbreak.
What Is EHV-1 and Why Is It So Dangerous?
EHV-1 is a common equine virus that can cause three types of disease:
- Respiratory illness
- Reproductive disease, including abortion in broodmares
- Neurologic disease, known as Equine Herpes Myeloencephalopathy (EHM)
The neurologic form is the most dangerous. Horses with EHM can decline rapidly, and outbreaks often result in movement restrictions, quarantines, and canceled events.
“Quarantining and reducing exposure is vital because the virus spreads easily and can transmit from horse to horse before any clinical signs appear,” said Dr. Jared Janke, clinical associate professor of equine internal medicine at the Texas A&M College of Veterinary Medicine and Biomedical Sciences. “Preventing the movement of exposed horses helps cut off main transmission routes.”
How EHV-1 Spreads in Barns
EHV-1 spreads through:
- Direct horse-to-horse contact
- Short-distance airborne transmission (less than 30 feet)
- Indirect transmission via people, clothing, equipment, trailers, water buckets, or grooming tools
The virus can survive in the environment for several weeks, making shared equipment and poor hygiene major risk factors during outbreaks.
Caregiver Action Steps
- Immediately isolate sick or exposed horses
- Stop horse movement in and out of the barn
- Do not share grooming tools, buckets, hoses, or tack
- Change clothes and wash hands and arms thoroughly after handling isolated horses
Clinical Signs Every Caregiver Should Watch For
Clinical signs usually appear within 5–10 days of infection, though neurologic cases may take longer.
Common Early Signs
- Fever (often intermittent)
- Lethargy
- Nasal discharge
- Coughing
“Fever is the most consistent sign identified in EHV-1 infections, but it is usually not persistent,” Janke said. “It can come and go throughout the day, so owners should conduct temperature readings at least twice daily.”
Neurologic (EHM) Warning Signs
- Hindlimb incoordination
- Weakness
- Urine dribbling (incontinence)
- Weak tail tone
- Reduced sensation around the tail and hindquarters
“The most concerning signs to watch for include fever, lethargy, limb incoordination, weakness, weak tail tone and urine dribbling,” Janke said. “These signs can progress to an inability to stand.”
Any horse showing fever plus neurologic signs should be treated as an emergency.
Diagnosis, Reporting, and Why Speed Matters
If EHV-1 is suspected:
- Isolate the horse immediately
- Stop all horse movement
- Contact your veterinarian right away
Diagnosis is typically made using a nasal swab and blood test, with results often available within one to two days. Because EHM is a reportable disease, veterinarians must notify state animal health officials to help prevent wider outbreaks.“Owners must recognize that EHM is a reportable disease because of its highly contagious nature and the serious effects outbreaks can have on the horse industry,” Janke said.
Treatment: Managing Symptoms and Supporting Recovery
There is no cure for EHV-1. Treatment focuses on supportive care, which may include:
- Anti-inflammatory medications
- Intravenous fluids
- Intensive nursing and monitoring
Antiviral medications may be considered, but evidence of their effectiveness is limited.
“When these medications are used, they appear to be most beneficial when initiated before clinical signs or at very early stages of disease,” Dr. Janke said.
Prognosis
- Overall survival rate in EHM outbreaks: 70–80%
- Horses that remain standing and show mild neurologic signs often recover
- Horses that become unable to stand face a much poorer prognosis
Recovered horses may still shed the virus, so repeat testing and extended quarantine are often required.
Prevention: The Most Powerful Tool Caregivers Have
While EHV-1 vaccines are widely available, no vaccine fully prevents neurologic disease.
Keeping the horse’s immune system strong is key, according to veterinarian Dr. Joyce Harman.
Best Prevention Practices
- Keep healthy horses away from infected or exposed horses
- Avoid travel during active outbreaks
- Take rectal temperatures twice daily during outbreak periods
- Isolate immediately at the first sign of fever
- Follow all guidance from your veterinarian and state animal health officials
“Contact your veterinarian as soon as possible if your horse has been in contact with or is suspected to have been exposed,” Janke said. “This gives you a better chance of intervening early before clinical signs have developed.”
Final Takeaway for Horse Caregivers
EHV-1 outbreaks demand vigilance, preparation, and rapid response. Caregivers who monitor closely, isolate quickly, and work closely with their veterinarian play a critical role in stopping the spread of this serious disease.
When it comes to EHV-1, early action saves horses.
