Recognizing the Signs of Equine Herpesvirus (EHV)

What Horse Owners Need to Know – From Oliver Mobile Veterinary Services

Equine herpesvirus (EHV) is a common virus; most horses are exposed at some point in their lives. In many cases, they show only mild or no signs, but in others, EHV can lead to serious respiratory illness, abortion, or a neurologic condition called equine herpesvirus myeloencephalopathy (EHM).

As a mobile equine practice serving northwest Ohio and southeast Michigan, Oliver Mobile Veterinary Services is committed to helping horse owners recognize the early signs of EHV and understand when to call for help.

What is EHV?

EHV is a family of viruses (EHV-1, EHV-3, EHV-4, and others). EHV-1 and EHV-4 are the most important for most barns:

• EHV-1 can cause respiratory disease, abortion, newborn foal illness, and neurologic disease.

• EHV-4 most often causes non-fatal upper respiratory infections, especially in young horses.

The neurologic form, EHM, happens when EHV-1 damages blood vessels in the brain and spinal cord, leading to sudden and sometimes severe neurologic signs.

How EHV Spreads

EHV primarily spreads through the respiratory route, especially nose-to-nose contact and droplets from coughs or sneezes. However, it can also travel on:

• Human hands and clothing

• Tack and grooming tools

• Trailers

• Feed and water buckets

The virus can survive in the environment for several days under typical barn conditions, so cleaning and disinfection are extremely important when there is concern about EHV.

Incubation Period

After a horse is exposed, the incubation period can be:

• As short as 24 hours

• Typically 4–6 days

• Occasionally up to 10 days

Because signs may be delayed, a horse can be shedding virus before anyone realizes it is sick.

Recognizing the Signs of Equine Herpesvirus (EHV)

The respiratory form of EHV often looks like a viral “cold,” especially in younger horses. Common signs include:

• Fever over 101.5°F

• Nasal discharge (clear at first, then thicker and yellow)

• Mild coughing

• Enlarged lymph nodes under the jaw

Any horse with a fever and respiratory signs should be isolated from barn mates and checked by a veterinarian.

Neurologic Signs of EHM

With the neurologic form, horses may show very few respiratory signs. Fever can be the only early warning, and then neurologic changes can develop quickly over 24–48 hours.

Clinical signs may include:

• Hind-end weakness or stumbling

• Incoordination or a “drunken” gait

• Toe dragging

• Loss of tail tone

• “Dog-sitting” or leaning on walls or fences for balance

• Urinary dribbling or difficulty urinating

• Inability to rise

Neurologic EHV is an emergency. Immediate veterinary care and strict biosecurity measures are critical to protect the rest of the barn.

When to Call Oliver Mobile Veterinary Services

Contact your veterinarian right away if:

• Your horse has a fever over 101.5°F, especially if multiple horses in the barn are affected.

• You see any of the neurologic signs listed above.

• Your horse recently attended a show, trail ride, sale, or clinic and then developed fever or respiratory signs.

At Oliver Mobile Veterinary Services, we can come to your farm to:

• Perform a physical exam and temperature checks on exposed horses

• Collect nasal swabs and blood samples for EHV testing

• Help set up isolation and hygiene protocols for your facility

• Discuss treatment options and supportive care plans

Prevention and Biosecurity

Good barn habits go a long way toward reducing the risk of EHV and other contagious diseases:

• Isolate new arrivals and horses returning from events.

• Take temperatures twice daily on sick or exposed horses and keep written logs.

• Do not share buckets, halters, or grooming tools between groups of horses.

• Clean and disinfect stalls, trailers, and equipment after sick or traveling horses use them.

• Work with your veterinarian on an appropriate vaccination and biosecurity plan for your specific facility.

Final Thoughts

EHV will likely always be present in the horse population, but serious outcomes can be reduced with early recognition, smart management, and strong barn biosecurity. If you have questions about EHV, want to review your farm’s protocols, or are concerned about a horse that may be showing signs, Oliver Mobile Veterinary Services is here to help.

To schedule a visit or discuss your concerns, call 419.345.1093 or visit olivermobilevet.com.