Equine Herpesvirus Infections: Treatment Progress and Challenges in Horses and Donkeys

Equine herpesvirus (EHV) infections represent a significant global veterinary and economic challenge affecting both horses and donkeys across all inhabited continents. This narrative review comprehensively examines the nine distinct EHV species (EHV-1 through EHV-9), their taxonomic classification within Alphaherpesvirinae and Gammaherpesvirinae subfamilies, and their diverse host tropism patterns. The complex molecular pathogenesis involves sophisticated viral glycoproteins (gK, gB, gC, gH, gM, gL, gG, gD, gI, gE) that orchestrate cellular invasion, immune evasion, and intercellular transmission. Clinical manifestations vary considerably, ranging from respiratory diseases and reproductive failures to severe neurological disorders, with EHV-1 demonstrating the most severe presentations including myeloencephalopathy. Global distribution analysis reveals widespread circulation across Europe, Asia, Africa, the Americas, and Oceania, with species-specific clinical patterns. Current therapeutic options remain largely supportive, with experimental compounds like berbamine and cepharanthine, celastrol, blebbistatin, and hyperoside showing promise in preclinical studies. Vaccination programs demonstrate limited effectiveness, failing to prevent transmission at population levels despite inducing individual immune responses. The sophisticated immune evasion strategies employed by EHVs, including the "Trojan horse" mechanism utilizing infected leukocytes, highlight the complexity of host-pathogen interactions and underscore the urgent need for innovative prevention and treatment strategies.