Pathogenesis of in utero infection: experimental infection of five-week-old porcine fetuses with porcine parvovirus.

Injection of porcine parvovirus (PPV) into the allantoic fluid of 3 or 4 fetuses of each of 4 litters of PPV-immune gilts early in gestation (34 to 36 days) resulted in fetal maceration and mummification. A high concentration of virus demonstrated in many tissues of fetuses collected 1 week after initial intraallantoic exposure indicated extensive viral replication. Progressively lesser amounts of virus were isolated from tissues of macerated and mummified fetuses collected after longer intervals; however, direct examination of many of the same tissues by immunofluorescence microscopy revealed masses of viral antigen throughout. Abortion was not a sequela of infection of fetuses of immune gilts nor was either virus or viral antigen ever demonstrated in maternal tissues, including those contiguous with infected fetuses. Intrauterine transmission of PPV from fetuses exposed by intraallantoic injection of virus was only confirmed for 2 of the 18 littermate controls that were tested.