Infectious causes of abortion in mares

Infectious abortions in mares often take place during the last term of gestation, and involve an important economic loss. Placentitis occurs due to the colonisation of the corion with bacteria or fungi, via the cervix (ascendant placentitis), haematogenous or by other routes. The diagnosis is carried out by measuring the placental thickness using ultrasounds; early treatment often has good results. The main causes of abortions with a viral etiology are Equine Herpesvirus-1/-4 (EHV) and Equine Viral Arteritis (EVA). EHV is endemic and is transmitted by the contact with infected animals and fomites. EVA causes abortions in mares with a primoinfection, the main reservoir of this disease are the asymptomatic stallions which excrete the virus in the semen. The main measures to prevent the occurrence of infectious abortions are: implementing adequate vaccination programmes, keeping pregnant mares in small groups, isolated from other animals, using semen and stallions tested against EVA and the isolation and investigation of any abortion cases in the premises.