Experimental transplacental infection of pregnant dogs with canine herpesvirus.

Fetal infection was established in 28 of 33 pups obtained from 7 pregnant dogs (47th to 53rd day of gestation) inoculated IV with canine herpesvirus (CHV). The pathogenesis of transplacental CHV infection was investigated by using pathologic examination, immunofluorescence microscopy, and viral assay. Infection with the virus was recognized in 13 of 18 neonatal pups obtained from 4 bitches by spontaneous delivery at full term. Eleven pups died within a week of birth and all had characteristic lesions of CHV infection. Thirteen live-born and 2 stillborn pups derived from 3 bitches by cesarean section died within 9 days of birth. Characteristic lesions of CHV infection were observed in various organs, such as liver, spleen, kidney, and lung. Fourteen of the fetal placentas had variable degree of necrotizing lesions. The lesions were characterized by degenerative changes and focal necrosis in the placental labyrinth. Lesions were present in the walls of allantoic blood vessels. Intranuclear inclusions were evident in degenerating trophoblast cells and in the cells of maternal and fetal blood vessels. Infective virus and viral antigen were detected in the various organs of pups and in the trophoblastic cells of junctional zone. Virus also was found in the walls of maternal and fetal blood vessels of the placental tissues. The results strongly indicated that transplacental transmission of CHV may occur in pregnant dogs at a late stage of gestation.