Abortogenic viruses in horses

Abstract

Summary Viral causes of abortion include equine viral arteritis (EVA) and infection with equine herpesviruses‐1 and ‐4 (EHV‐1 and EHV‐4). Transmission of equine arteritis virus (EAV) occurs through respiratory, venereal or transplacental routes. Horizontal respiratory transmission of EAV results from exposure to infective nasopharyngeal secretions from acutely infected horses. For this transmission to occur, direct and close contact between horses is necessary. Venereal infection is an efficient method of transmission, with seroconversion of 85 to 100% of seronegative mares bred to virus shedding stallions. Asymptomatic carrier stallions are the essential natural reservoir of equine arteritis virus. Equine herpesviruses‐1 and ‐4 infect a susceptible host, replicate and establish a lifelong latent infection without any associated clinical signs. Reactivation of latent infections can result from factors such as stress and intercurrent disease. The control of these diseases is by implementation of appropriate management and hygiene measures, supplemented by vaccination and, in the case of EVA, by the identification of persistently infected stallions, which can be removed from breeding or continue to be bred to if managed under controlled conditions to prevent the risk of an outbreak of the disease.

Equid herpesvirus 8: Complete genome sequence and association with abortion in mares

“…Indeed, the EHV-8 strains isolated from two aborted foetuses of horses in this study were identified incorrectly as EHV-1 during initial testing, due to cross reactivity of the PCR assay. Viral causes of abortion in horses have only been attributed to EHV-1, and less frequently EHV-4 and equine viral arteritis [ 47 ]. In future, EHV- 8 will need to be included in the differential diagnosis.…”

Virological examination of conjunctival swabs in clinically healthy horses

“…Moreover, equine herpesvirus type 2 has an affinity for conjunctival epithelial cells (4). Other viruses can also cause conjunctivitis in horses: Equine Arteriritis Virus (EAV), Equine Influenza Virus (EIV) or less frequently adenoviruses (2,3,6,7). The most common ocular signs include eye discharge (mucous to purulent), redness and conjunctival oedema and photophobia (6).…”

Pathology of equine amnionitis and foetal lLoss: clinical and experimental studies

“…Equine herpesvirus 1 (EHV-1) can cause sporadic or "storms" of abortions worldwide Hong et al, 1993a;Smith et al, 2003;Szeredi et al, 2008;Butt and Carrick, 2010;Bażanów et al, 2014). The virus initially infects the mare via the respiratory tract with a subsequent viremia allowing infection of the endometrial vascular endothelial cells at the base of the microcotyledans (Lunn et al, 2009).…”

“…Foetuses are usually aborted from mid to late gestation due to an increased susceptibility of the uterine endothelial cells to the virus during this period (Bażanów et al, 2014). Foals may be stillborn after sudden expulsion and are often still within the amniotic sac (Bażanów et al, 2014).…”

“…Foals may be stillborn after sudden expulsion and are often still within the amniotic sac (Bażanów et al, 2014). Grossly the placenta may be normal or be slightly oedematous and the foetus may have pulmonary oedema, petechiae, subcutaneous oedema and/or excess pleural and abdominal fluid (Donaldson, 2003).…”