PORENCEPHALY, HYDRANENCEPHALY AND LEUKOENCEPHALOPATHY IN OVINE FETUSES FOLLOWING TRANSPLACENTAL INFECTION WITH BOVINE VIRUS DIARRHEA VIRUS - DISTRIBUTION OF VIRAL-ANTIGEN AND CHARACTERIZATION OF CELLULAR-RESPONSE

The distribution of viral antigen, histological lesions and inflammato ry responses were examined in brains from ovine fetuses following expe rimental transplacental infection with a cytopathogenic strain of bovi ne virus diarrhoea virus (BVDV). At 10 and 14 days post inoculation (p .i.) viral antigen-containing cells were found throughout the differen t zones of the developing telencephalon and cerebellum. Corresponding to the distribution of viral antigen, necrotic lesions both of already differentiated and of undifferentiated fetal brain cells occurred. Th e extent and severity of microscopic lesions correlated positively wit h the number of viral antigen-containing cells. The destructive lesion s were accompanied by meningeal and parenchymal cellular infiltrations predominantly with phagocytosing macrophages. In fetuses examined at 21 days p.i. a massive necrosis of the cerebral hemispheres and severe infiltrations with macrophages and CD3-positive lymphocytes had devel oped. In fetuses studied between 32 and 80 days p.i. porencephaly, hyd ranencephaly and leukoencephalomalacic lesions were present. In brain tissue of these fetuses, with the exception of two cases, BVD viral an tigen was no longer detected.