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EHV-1: What Horse Owners Need to Know

What is EHV-1? Learn the signs of this contagious and potentially life-threatening virus and how to keep your horse safe.
gray and bay arabian horses wearing traditional bridles sniff and touch noses
EHV-1 can be transmitted by direct contact between horses, air droplets, or nasal discharge. | Getty Images

If you plan to show your horse or even just take him off-property, you’ll want to have equine herpesvirus-1 (EHV-1) on your radar. This highly contagious virus can cause a range of clinical signs, from mild fever to severe neurologic problems. In rare cases it can even be fatal.

EHV-1 can be transmitted by direct contact between horses, air droplets, or nasal discharge from infected horses. It can also be spread through contact with contaminated items such as tack and grooming tools, buckets and mangers, or stable or stall surfaces. In addition, humans can transmit the virus from one horse to another on their skin, clothing, or footwear. This virus can live for weeks on surfaces, so take great care around infected horses to keep it contained. EHV-1 is common and can be present in horses for years before it manifests, if it ever does. Stressful situations such as strenuous exercise, weaning, or long-distance travel can spur an outbreak.

Let’s learn more about EHV-1, including what signs to watch for and how you can help protect your horse.

Clinical Signs of EHV

Symptoms of EHV-1 include:

  • Fever
  • Respiratory disease
  • Cough
  • Nasal discharge
  • Abortion in pregnant mares
  • Neurologic signs, including incoordination and inability to balance

Horses with EHV-1 that exhibit neurologic signs are considered equine herpesvirus myeloencephalopathy (EHM) positive, which puts nearby horses at greater risk. EHM-positive horses will show incoordination of limbs and weakness in the hind end, and the disease is usually fatal. A horse that lives through it will most likely experience ongoing neurologic issues.

What You Can Do

a bay horse with a blaze peers through the metal bars of a fenced paddock.
If your horse tests positive or shows signs of illness, isolate him from all other horses and take biosecurity precautions to keep the virus from spreading. | Getty Images

Keep these things in mind if your horse has been exposed to affected horses:

  1. Signs of illness usually appear four to six days after exposure to EHV-1 but can appear within 24 hours. If you see symptoms of EHV-1 or know your horse has been in contact with an infected horse or facility, have your veterinarian take a nasal swab or blood sample to test for it. 
  2. For horses with EHV-1, a veterinarian might prescribe anti-inflammatory drugs; for horses with EHM, antiviral medications. 
  3. Prevention is key. If your horse shows signs of illness, keep him home and away from other horses. If he tests positive, isolate him from all other horses and take biosecurity precautions when caring for him to keep the virus from spreading. If you’re away from home or traveling with your horse when encountering EHV-1, do not enter or depart a facility until cleared by a veterinarian. 
  4. Your veterinarian can administer a vaccine to protect against respiratory and abortion manifestations of EHV-1, but current vaccines don’t prevent EHM. Some horse shows, events, and boarding facilities require vaccination before allowing your horse to participate or move in. 

Biosecurity and EHV-1 Prevention

Here are some smart biosecurity steps you can take to protect your horse and limit disease spread.

a woman's hand holding a water horse filling a blue bucket in  a horse barn
When filling water containers, don’t allow the hose nozzle to touch the container. | Courtesy The Horse Staff
At Home
  • Work with your vet to set up a vaccination plan for all horses in your care.
  • Be sure all horses entering your facility (or the one where your horse is boarded) are appropriately vaccinated and free of all communicable diseases. Ideally, isolate all incoming horses for up to 30 days.
  • Don’t share water or feed buckets, grooming equipment, or any piece of gear that may come in contact with a horse’s eyes, nose, or mouth.
  • When cleaning or filling water containers, don’t allow the hose nozzle to touch the container.
  • Remove all manure/waste products to a location away from the barn.
  • Limit horses’ exposure to disease-spreading pests such as flies and mosquitoes.

On the Road
  • Monitor temperatures before traveling, and don’t ship a horse that’s had a fever within five days of a haul.
  • Keep a disinfectant-filled spray bottle handy to disinfect stalls and stable areas before moving your horse onto show grounds or other new facilities (spray liberally!).
  • Don’t use common water buckets or feed areas at shows or event grounds.
  • Don’t borrow/share halters, twitches, lip chains, or other items that may touch a horse’s eyes, nose, or mouth.

Watch: How To Take a Horse’s Temperature

How to Disinfect
  • Items you can disinfect when necessary include nylon halters, bits, lip chains, grooming equipment, stalls, buckets, shovels, pitchforks, and even shoes and car/truck tires.
  • Remove all excess dirt/debris from items to be disinfected, including stall floors and walls.
  • Wash the item or area first with laundry detergent or dish soap.
  • Immerse or thoroughly wet the item/area with an appropriate disinfectant. Phenolic-based (Lysol) or quaternary ammonium-based (Roccal D) products are most effective. (Although bleach is effective against most viruses and bacteria, it’s inactivated by organic material, making it less than ideal in a barn situation.)
  • Rinse the disinfectant off thoroughly with plain water.

Take-Home Message

EHV-1 is a serious concern for horse owners. With proper knowledge and preventive measures, however, you can help keep your horse safe. Stay up to date on the latest EHV-1 information and follow recommended biosecurity practices to minimize the risk of transmission. If you suspect your horse was exposed to EHV-1 or is exhibiting any symptoms, contact your veterinarian right away.

This content originally appeared on Horse&Rider.

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