Equine coital exanthema: New approaches to minimise the negative impact on the equine industry

Abstract

Equine coital exanthema (ECE), caused by Equid alphaherpesvirus 3 (EHV-3), is a highlycontagious, venereally transmitted mucocutaneous disease, characterised by the formation of papules, vesicles, pustules and ulcers on the external genital organs of mares andstallions. The infection is endemic worldwide, and the virus is transmitted mainly throughdirect contact during sexual intercourse and by contaminated instruments during reproductive manoeuvres in breeding facilities. The only known biological reservoir of EHV-3is the latently infected horse; it is well-known that, as for other herpesviral infections,periods of reactivation from latency, with production and shedding of infectious virus, arethe source of infection for other comingling susceptible animals. Episodes of reactivationand shedding, either with or without clinical manifestation, and together with variablelevels of serum antibodies, have been observed. Although the disease is relatively benignand does not result in systemic illness, infertility or abortion, it does have a negativeimpact on the equine industry, as it forces to temporarily withdraw affected animals,consequently disrupting mating activities in breeding enterprises. Thus, outbreaks of ECEcontinue to be a major problem for the equine industry, mostly in those facilities withheavily scheduled breeding calendars during reproductive seasons. For affected stallions,such disruptions may translate into significant end-of-season decreases in the mare-booksize. Similarly, affected mares may miss breeding opportunities. In artificial inseminationand embryo transfer centres, affected mares may be reluctant to be inspected, inseminated or transferred, with the consequent loss of opportunities to become pregnant. Inboth scenarios (natural mating or artificial insemination), delayed foaling dates or reducedpregnancy rates may occur in mares that miss breeding opportunities because of thedisease. In the interest of reducing the negative impact of EHV-3 infections on breedingcentres, advances have been made during the last years as to diagnostic methodologies,treatment and prevention.