Equine picornaviruses: well known but poorly understood

Of the many members that comprise the family Picornaviridae, only two species are known to infect horses: equine rhinitis A virus (ERAV) and equine rhinitis B virus (ERBV). Each species now occupies a distinct phylogenetic branch within the family, with the single serotype of ERAV grouping with the aphthoviruses, such as foot-and-mouth disease virus (FMDV), and the three serotypes of ERBV as the sole members of the genus Erbovirus. The high seroprevalence of equine picornaviruses in horse populations worldwide contrasts with the relatively few reports of detection of these viruses and poor understanding of their contribution to disease. This review examines the current knowledge regarding the distribution and pathogenesis of these viruses and discusses recent advances in diagnostic methods that may lead to a better understanding of the role of these viruses as contributors to equine respiratory disease.