The role of endothelial cell infection in the endometrium, placenta and foetus of equid herpesvirus 1 (EHV-1) abortions.

One of three mares in the last trimester of pregnancy became paraplegic 7 days after experimental infection with EHV-1 and was killed 10 days after infection (d.p.i.). The other two mares aborted foetuses at 12 and 14 d.p.i. In the first mare, virus was detected by immunofluorescence (IIF) and immunoperoxidase (IP) staining in endothelial cells of the endometrium, placenta and umbilical vein, but not in any other foetal tissues. In the experimentally aborted foetuses, and in two other independent field cases of abortions, endothelial cell infection was also detected in the foetuses, both in major blood vessels and in capillaries or sinusoidal cells associated with parenchymal lesions. In these four cases there were also positive endothelial placental lesions detected by IIF or IP, although it was not always possible to isolate virus from these tissues, as it was from the foetuses. The evidence suggests that infection of maternal endothelial cells has a major role in the pathogenesis of abortion, and that endothelial cells are also involved in dissemination of virus within the foetus.