EXPERIMENTAL PLACENTAL-TRANSFER OF FOOT-AND-MOUTH-DISEASE VIRUS IN MICE

Abstract

An attenuated type O foot-and-mouth disease (FMD) virus which was virulent for infant, but not for pregnant, mice was superior to a virulent type C FMD virus in the development of a model system for the study of placental transfer of FMD in mice. When mice were inoculated at day 8 or 12 of gestation with type O FMD virus, the virus was detectable in the maternal pancreas for 3 days and in the placenta for 6 days. Viral levels in the fetus and the amniotic fluid were inconsistent and were apparently due to a spillover from the placental infection. The elimination of the virus from the placenta coincided with the expected production of maternal 7S antibody. Mice inoculated from days 0-12 of gestation did not have a significant increase in dead young by day 18 (the day of necropsy). Similarly inoculated mice, when permitted to go to term, produced and raised normal-size litters. Inoculation on day 15 of gestation resulted in an increased number of deaths due to morbidity of the dams. The placenta evidently serves as an active site of infection for FMD virus in pregnant mice, but the fetus is apparently relatively resistant to infection. [These results may have implications to bovine abortions caused by FMD.].