ABSTRACT
Electron microscopic analysis of the equine rhinopneumonitis virus revealed the morphology of a equine herpesvirus type 1 (EHV-1). The natural host range for EHV-1 is the Equidae family although virus replication has been shown in kittens, rabbit cornea, baby mice, and on the chorioallantoic membrane of embryonated eggs. The pathologic lesions found in aborted fetuses are also very characteristic of EHV-1 infections and have been described by numerous investigators. Fetal membranes are expelled with the fetus or quickly after the abortion, and the mares do not suffer any uterine infections, and will breed back as quickly as if they had given birth to a full term live foal. The attenuated vaccine was produced in Syrian hamsters and has been used by intranasal inoculation in the mares, and the strain that was used would still produce abortion if inoculated directly into the fetus, but would confer protection and had a reduced virulence when used intranasally.
