Equine viral arteritis is a virus disease of horses, donkeys, and zebras and occurs in many countries, especially in Europe and the USA. It is also known as “pinkeye”. Virus isolation was first successful in 1953 from abortion material in Bucyrus, USA. Based on the characteristic inflammation and changes observed in blood vessels the virus was given the name equine arteritis virus (EAV). The enveloped, positive-sense single-stranded RNA virus is classified into the genus Arterivirus of the family Arteriviridae together with the lactate dehydrogenase elevating virus (LDV), the porcine reproductive and respiratory syndrome virus (PRRSV) and the Simian haemorrhagic fever virus (SHFV).
EAV is transmitted by direct contact with acutely infected animals especially via aerosols and secretions from the respiratory tract. Transmission via lacrimal fluid, blood, urine and feces is also possible. In EAV-induced abortion, the aborted fetal materials which contain a high viral load are an important source of infection. Another significant transmission route is the venereal spread of the virus. During the acute phase of infection, mares excrete EAV via vaginal secretions. In infected stallions the virus persists in the accessory sex glands (prostate, seminal vesicle) over long periods of time and is excreted into the seminal fluid, while in geldings and mares virus excretion stops as soon as the acute infection has resolved. However 30 to 40 % of EAV positive stallions will become chronic virus excretors; short-term (2 to 5 weeks), intermediary (3 to 8 months) and long-term excretors (years to lifelong) are distinguished. These stallions are the natural virus reservoir and play an important role in the spread of the virus.
After initial replication in alveolar macrophages, EAV is spread via the blood circulation and infects macrophages and endothelia of blood and lymphatic vessels. Generalized necroses, especially of the small arteries, lead to increased vessel permeability with haemorrhages and edema especially of the hind legs and hypogastrium. Most natural EAV infections remain asymptomatic, however isolated cases with fatal outcome are observed. Especially foals, horses in a bad nutritional condition, horses with parasitic infestation as well as pregnant mares may develop high fever, distinct respiratory disease with severe nasal and ocular discharge (conjunctivitis) as well as symptoms of colic. Furthermore, direct damage of the fetus or changes of the uterus or placenta may lead to abortion or premature birth or to the birth of weak animals.
In Germany, a licensed inactivated vaccine for immunoprophylaxis is available.