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Equine viral arteritis virus





  • Family: Arteriviridae.
  • Genus: Equartevirus.
  • Species: Equine arteritis virus.

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Clinical Effects



  • Carrier stallions.
  • 10-70 % of infected stallions become persistently infected and shed virus continuously in the semen.


  • Aerosol spread; inhalation.
  • Venereal route important by acutely infected stallions or mares and persistently infected stallions.
  • Indirect contact through virus contaminated fomites.

Pathological effects

  • Neutralizing antibody develops within 2 weeks of infection.
  • Recovered animals are solidly immune.
  • Incubation period 2-13 days.
  • Virus replicates mainly in macrophages and epithelial cells.
  • Virus causes necrosis of intestinal cells and muscle cells in arterial media → adventitial edema → lesions occur in small arteries of approximately 0.5 mm diameter, especially in intestines, spleen, lymph nodes, and adrenal capsule Equine viral arteritis (EVA).
  • Vascular changes may cause edema of ventral body wall and limbs.
  • Conjunctivitis Conjunctivitis: overview and palpebral edema → 'pink eye'.
  • Abortion may result from uterine lesions Abortion: overview.

Other Host Effects

  • Many infections are subclinical; may be due to avirulent strains of virus.


Control via animal

  • No specific treatment available.

Control via chemotherapies

  • Symptomatic.


  • Tissue-culture attenuated live virus vaccine has been used, but may cause mild febrile reaction Equine viral arteritis vaccine. Not recommended for pregnant mares, especially during last 2 months of gestation (only available in Canada and US).
  • The MLV vaccine stimulates a strongly protective immune response.
  • Inactivated whole virus adjuvanted vaccines - duration of protection unknown.


Consult the Codes of Practice for control of  Equine Viral Arteritis (British Horseracing Board) - issued annually - before using any vaccine.

Other countermeasures

  • Isolate carrier stallions, breed only to mares naturally seropositive for antibodies to the virus or vaccinated not less than 3 weeks previously; isolate these mares for 3 weeks after breeding.
  • Carrier stallions - screen first serologically; if positive, attempt virus isolation or detection (first season stallions). Vaccinate at-risk breeding stallions.


  • The modified live virus vaccine stimulates a strongly protective immune response.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Barbacini S (2005) An outbreak of equine arteritis virus infection in a stallion at a Trakehner studfarm. Equine Vet Educ 17 (6), 294-296 VetMedResource.
  • Wood J L N & Newton J R (2005) The continuing challenge of EVA. Equine Vet Educ 17 (6), 297-298 VetMedResource.
  • Guthrie A J, Howell P G et al (2003) Lateral transmission of equine areritis virus among Lipizzaner stallions in South Africa. Equine Vet J 35 (6), 596-600 PubMed.
  • Szeredi L, Hornyak A, Denes B & Rusvai M (2003) Equine viral arteritis in a newborn foal: parallel detection of the virus by immunohistochemistry, polymerase chain reaction and virus isolation. J Vet Med B Infect Dis Vet Public Health 50 (6), 270-274 PubMed.
  • Wood J L N, Chirnside E D, Mumford J A & Higgins A J (1995) First recorded outbreak of equine viral arteritis in the United Kingdom. Vet Rec 136 (15), 381-385.
  • Chirnside E D (1992) Equine arteritis virus - an overview. British Vet J 148 (3), 181-197.

Other sources of information

  • Horserace Betting Levy Board (2019) Codes of Practice. 5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email:; Website:

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