Equine gammaherpesviruses Pathogenesis, epidemiology and diagnosis

Equine gammaherpesviruses (gamma EHV) have been widely studied over the past 45 years and many isolates have been characterised Despite this the diagnosis of gamma EHV infection remains difficult to establish as its clinical manifestations lack specificity ranging from mild respiratory signs in a small number of animals to outbreaks in large groups of young horses This review focuses on the epidemiology pathogenesis clinical manifestations and diagnosis of equine herpesvirus (EHV) 2 and -5 infections as well as on the genetic variation of these viruses Study of these variations has resulted in hypotheses relating to viral re-Infection and re-activation Interestingly the viruses were found to contain genetic sequences identical to those of eukaryotic cells which are considered central to the development of viral latency through interfering with host immune and inflammatory responses Future molecular biological studies will further elucidate the virulence mechanisms of these equine pathogens (c) 2009 Elsevier Ltd All rights reserved