Equine Herpesviruses 2 and 5

Equids may be infected by at least 11 different herpesviruses. These viruses were probably divided into three sub-families in the era of the dinosaurs, which makes these viruses among the oldest and then the most adapted to their hosts. The host (Equus caballus) may contract various diseases in primary infection or reactivation caused by one or more of the five herpesviruses that might be detected throughout his life or athletic career. Among these five viruses, two families differ in terms of virological (and partly at the genomic level) and will bring the clinician dealing with varied challenges. Alphaherpesviruses (EHV-1 and EHV-4) are viruses which rapid replication causes significant tissue damages (kytic phase) by triggering, notably during primary infection, inflammatory responses and clinical signs occasionally severe in young or adult horses. Gammaherpesviruses (EHV-2 and EHV-5) are viruses which pathogenicity is still illdefined, with irregular expression of clinical signs. One common point among these infectious agents is their capacity of “latency” within the host (leukocytes cell line and ganglia) following the first natural contact. These “latent” viruses may be reactivated thanks to various mechanisms such as stress, intercurrent disease, contact with new viral strains or any cause of immunosuppression. […]