This project aims to develop a live attenuated vaccine to protect horses against equine herpesvirus 1 (EHV-1)-associated diseases by intranasal administration. This vaccine will protect the upper respiratory tract (primary replication site of EHV-1) of horses by the activation of a local and general immunity. The proposed vaccine strain will have a plugin spot for the introduction of other foreign (viral) genes, which allows to use this strain as a vector to vaccinate against other (viral) pathogens. Moreover, because a foreign gene replaces an EHV-1 gene, this approach allows to differentiate formerly vaccinated and infected horses (marker vaccine; DIVA principle).