Virus-induced abortion. Studies of equine herpesvirus 1 (abortion virus) in hamsters.

A hamster-adapted strain of equine herpesvirus-1 (equine abortion virus) caused severe hepatic degeneration in both pregnant and nonpregnant hamsters and, in addition, regularly induced abortion in pregnant hamsters inoculated at midgestation. In nonpregnant hamsters, the only consistently affected organ was the liver despite a prolonged viremia. Newborn animals usually died 1 to 2 days after inoculation; adults died 5 to 9 days after inoculation. In pregnant hamsters, the virus had a tropism for the placenta as well as the liver. The placental infection was confined almost exclusively to one cell type in the fetal portion of the placenta: the trophoblast cells of the syncytiotrophoblast zone. Necrosis of this zone led to fetal death and abortion. Infection of the fetus did not occur.