The nucleotide sequence of the glycoprotein G homologue of equine herpesvirus 3 (EHV3) indicates EHV3 is a distinct equid alphaherpesvirus.

EHV3 causes equine coital exanthema and has been classified as an alphaherpesvirus on the basis of its biological properties; however due to the absence of any sequence information the phylogenetic relationship has not previously been examined. The complete nucleotide sequence of the EHV3 glycoprotein G (gG) gene was determined and showed that this virus is most closely related to the alphaherpesviruses equine herpesviruses type 1 (EHV 1) and type 4 (EHV4). EHV3 gG contains conserved and variable regions which are homologous to those previously defined for EHV1 and EHV4 gG proteins. Consistent with EHV1 and EHV4 gG, the variable region of EHV3 gG was found to elicit a strong antibody response in experimentally and naturally infected horses and could be exploited for use as a diagnostic reagent.