Equine Viral Arteritis: Symptoms, Treatment, and Prevention Options

Equine viral arteritis (EVA) is a serious and contagious viral infection caused by the equine arteritis virus. The disease is found in horses around the world and can severely affect horse breeding.

What Is Equine Viral Arteritis?

EVA infections vary widely between countries and among horse breeds, but the highest infection rate is seen in Standardbreds and warmbloods.

Within the equine population, colts and stallions are most often responsible for carrying the virus. Unvaccinated pregnant mares are most vulnerable to EVA, which may lead to abortions (miscarriages). Newborn foals can develop pneumonia from EVA, which can be fatal.

While any horse can develop EVA, the biggest impact is to breeders, racehorse owners, and show horses because it can severely affect breeding and international movement of horses and semen.

EVA in horses is a reportable disease, meaning veterinarians and horse owners are legally required to report any suspected cases to the state animal health department or USDA.

Many horses with EVA may have few to no symptoms, so it is often not a medical emergency. However, if you suspect your horse may have EVA, consult your veterinarian.

Symptoms of Equine Viral Arteritis

For most cases of EVA, horses will have little to no symptoms. After a horse has been infected by EVA, clinical signs generally arise two to 14 days later.

When symptoms do occur, they can vary greatly and include respiratory signs, behavioral changes, vision problems, changes in gait, physical signs, and reproductive issues. Some examples include:

Respiratory Signs

• Nasal discharge

• Coughing

• Difficulty breathing

Behavioral Changes

• Depression

• Anorexia (not eating)

Visions Problems

• Eye discharge

• Redness of the eye or tissues around the eye

• Swelling around the eye

• Squinting

• Cloudiness

Changes in Gait

• Ataxia (uncoordinated gait)

• Stiff gait

Systemic Signs

• Swelling of the limbs

• Swollen glands

• Hives

• Fever

• Depression

• Anorexia (not eating)

• Yellowing of the skin, eyes, or gums

• Colic

• Diarrhea

• Red spots on the gums

• Enlarged lymph nodes

Reproductive Signs

• Abortion

• Reduced fertility in stallions

Causes of Equine Viral Arteritis

Equine viral arteritis can spread through direct and close contact between horses, indirect transmission, and during breeding.

• Direct contact transmission in horses means it can pass from one horse to another through contact like respiratory droplets in the air.

• Indirect transmission can include transmission from contaminated objects such as tack, equipment, and feed or water buckets.

• Transmission during breeding can be direct contact during live cover breeding or indirect contact through artificial insemination, because the virus can shed in semen.

How Veterinarians Diagnose Equine Viral Arteritis

Equine viral arteritis is diagnosed by a veterinarian through examination, laboratory tests, and diagnostics.

The gold standard test for diagnosing EVA is virus isolation by sampling through blood tests, nasal swabs, and semen evaluation. Samples should be collected as soon as symptoms begin to help with an accurate diagnosis.

Post-mortem exams can be performed in fatal cases to confirm EVA as the cause.

Your veterinarian may ask questions about traveling, any new horses on the property, or breeding to better understand the potential risk of EVA or source of outbreak if confirmed positive.

How Do You Treat Equine Viral Arteritis in Horses?

The good news is that most cases of EVA do not require any treatment, and horses recover without complications or lasting effects.

If horses do require treatment, it is often supportive care. These treatments may include:

• Anti-inflammatory medications (Banamine)

• Medications to help with fever (Vetameg)

• Diuretics to eliminate fluid or prevent swelling (Salix)

• Rest from exercise

• Nutritional support

• Antibiotics

Recovery and Management of Equine Viral Arteritis

Most horses recover from EVA in one to two weeks, but this greatly depends on the severity of the symptoms and disease of each horse. 

Generally, a horse with EVA will not need any medications and will recover on their own. For a stallion with a persistent infection of EVA, surgical castration is the only option for effective treatment.

During an EVA outbreak, strict biosecurity measures should be followed. Recommended measures include:

• Isolating infected animals so the virus does not spread to other horses

• Testing and vaccinating horses

• Implementing proper breeding protocols

Equine Viral Arteritis Prevention

As a horse owner, the best way to prevent the spread of EVA is to vaccinate your horse and test any stallions to detect the virus prior to breeding.

The EVA vaccine for horses is recommended for use in healthy, non-stressed horses to help prevent abortion and respiratory infection associated with EVA.