EHV-1-induced abortion in mice and its relationship to stage of gestation.

The most important consequence of equine herpesvirus-1 (EHV-1) infection is abortion. The object of the present study was to characteristic further a murine EHV-1 abortion model and to make comparisons with the natural host with particular reference to the stage of gestation during which the infection occurs. BALB/c mice at different stages of pregnancy were infected intranasally with EHV-1 (strain AB4); they suffered respiratory distress, weight loss, and other constitutional signs of infection. When the virus was inoculated in the late second or early third week of gestation dead or dying fetuses were aborted, whereas infection between seven and nine days of pregnancy led to fetal death and resorption. During the process of resorption, complications were observed. Virus was frequently isolated from the placentas and occasionally from the tissues of the aborting fetuses, depending on the severity of the infection of the placentas. In some cases, therefore, the inoculation resulted in abortion although the infection was restricted to the placenta. Virus antigen was detected in the placentas, lungs and occasionally in other tissues of the aborting fetuses. The potential of this murine model for testing methods for the diagnosis and control of equine abortion is discussed.