Equine Viral Arteritis

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Equine viral arteritis is primarily a respiratory disease, but can be transmitted during breeding. Although it causes no clinical signs in many horses, it may cause respiratory infections, abortion in pregnant mares, and severe swelling of the legs, causing lameness. The incubation period varies from 2 to 13 days, with an average incubation period of 7 days.

Stallions are long-term carriers and shedders of the disease because the virus is testosterone-dependent, and the virus may become established in the secondary sex glands. Stallions may also spread the virus by the respiratory route during the first weeks after the initial infection. Mares, geldings, and foals that are infected may shed the virus for a couple of weeks, but virus transmission usually ends within three weeks.

Halters, other tack, water buckets, corral fences, transport trailers, and anything a horse can breathe on may become contaminated with the virus, and it may be transmitted to other horses in close proximity when they breath in the virus.


  • Difficulty breathing
  • Muscle soreness
  • Fever
  • Nasal discharge
  • Loss of appetite
  • Skin rash
  • Conjunctivitis
  • Depression
  • Abortion
  • Swollen limbs and genitals
  • Swollen mammary glands in mares
  • Skin rash or hives


Equine viral arteritis is caused by a virus that causes inflammation of horse's arteries, an RNA virus in the genus Arterivirus (family Arteriviridae). Antibodies to this virus which show that a horse has been infected with the virus are found in horses and zebras. Standard breds seem to be particularly susceptible to the disease.


Control of EVA can be achieved through movement restrictions and vaccination. A safe, effective, and low-cost vaccine is now available. Combining this vaccine with isolation of horses that may have been exposed to the virus by the venereal or respiratory route will greatly reduce the spread of the disease.

Quarantine of in-contact animals and disinfection of all areas where these horses are kept are critical in preventing its spread. Enveloped viruses can be destroyed by most common disinfectants.

Blood samples for EVA testing should be collected from all horses before breeding, and virus isolation tests should be performed on imported semen before use. Strict hygiene and disinfection of instruments and equipment are essential to minimize spread of the virus.

Yearly boosters should be given to all horses to protect against infection.


The symptoms of this disease may be difficult to differentiate from other equine respiratory illnesses. EVA can be diagnosed by virus isolation or serology. Nasal secretions, blood, semen, and tissues can be used for the tests.

Treatment includes rest and, in some cases, antibiotics to decrease the risk of secondary bacterial infection. Horses with the disease should be immediately isolated and good husbandry practices observed, including plenty of fresh water, good quality hay, a ventilated stall, and a warm blanket if the weather is cold.

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EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.