Necrotic Oophoritis in Gilts Associated with Experimental Inoculation of a Viral Gene-deletion Mutant Pseudorabies Vaccine

Previous work on the reproductive effects of various herpesviruses has demonstrated adverse effects on reproductive function in several host species. Although herpesviral vaccines are used in several species to ameliorate the clinical effects of infection, pathogenicity for reproductive tissue, associated with diminished reproductive efficiency, has been reported to be retained in a live-attenuated vaccine strain of the herpesvirus, bovine herpesvirus-1. The objective of this study was to determine if a gene-deletion mutant, thymidine kinase negative, pseudorabies virus retained acute pathogenicity for the reproductive tract of swine following intravenous inoculation during estrus. Estrous cycles of nulliparous gilts were synchronized by administration of a gonadotropin and daily exposure to a boar. During estrus, six gilts were inoculated intravenously with twice the recommended intramuscular dose of a commercially available viral gene-deletion mutant pseudorabies vaccine. Six control gilts in estrus were sham inoculated intravenously with vaccine diluent during estrus. All animals were euthanatized 10 days postinoculation, and the ovaries and uterus were collected for histopathology following gross examination. All reproductive tracts were grossly normal. Histologically, four of six treated gilts had a mild to moderate, multifocal, necrotizing oophoritis, with the lesions limited to corpora lutea and the adjacent stroma. Ovaries of control gilts exhibited no necrotizing lesions. Both control and pseudorabies vaccine-inoculated gilts had occasional minimal focal mononuclear infiltrates in the ovaries. These data show that live attenuated viral gene-deletion mutant pseudorabies vaccine administered to swine during estrus can result in acute pathogenicity in ovarian corpora lutea. No endocrinologic data is available in these pigs, so the impact on pregnancy maintenance is unknown.