Equine herpetic infection: features of pathogenesis and diagnosis
Equine alphaherpesviruses ― causative agents of rhinopneumonitis−viral abortion (EHV-1) and rhinopneumonitis (EHV-4) ― represent the subfamily Alphaherpesvirinae, genus Varicellovirus. EHV-1 causes abortion, respiratory pathology, and neurological disorders in horses of different ages. EHV-4 causes predominantly respiratory disease in foals and sporadic abortions in mares. In the etiopathogenesis of herpesvirus infections EHV-1 and EHV-4, the determining factors are pronounced tropism to epithelial cells, persistence in a non-replicative form, and unpredictable reactivation of a persistent virus with its release into the environment. EHV-1 and EHV-4 have similar antigenic determinants and cross-react in serological reactions. The high level of antigenic relationship between EHV-1 and EHV-4 can make it difficult to interpret serologic results in natural infections. The EHV-1 and EHV-4 strains in active circulation are genetically rather conservative. The exception is the new EHV-1 strains with a mutation in the gene encoding viral DNA polymerase, which caused outbreaks of neuroparalytic disease in some European countries and the United States. In several cases, the neurological syndrome has been reported due to use of some commercial vaccines