INFLUENCE OF VACCINE MEDIUM AND VACCINATION SCHEDULES ON THE INDUCTION OF ACTIVE IMMUNITY AGAINST AUJESZKYS-DISEASE IN MATERNALLY IMMUNE PIGS

Active immunity against Aujeszky's disease virus (ADV) was compared at the end of the fattening period in pigs which had been vaccinated wit h the attenuated Bartha strain according to different schedules in the presence of different levels of maternal immunity. The percentage of seropositive pigs at the end of the fattening period varied from 21 to 94 per cent. The percentage was significantly higher when the vaccina tion schedules were applied to pigs from mothers vaccinated with an at tenuated strain compared to pigs from mothers vaccinated with a subuni t vaccine or from infected-immune mothers. Additionally, this percenta ge was two to three times lower when pigs were vaccinated once at 10 w eeks old compared to pigs either revaccinated at 14 weeks or vaccinate d once at 14 weeks old. When the virus strain used for vaccination had been suspended either in saline or in an oil-in-water emulsion, signi ficant differences mere not found in the serological response after va ccination and in the reduction of virus excretion upon subsequent chal lenge. In challenge experiments, a significantly longer duration of vi rus excretion was observed in vaccinated pigs which had not seroconver ted than in vaccinated but seropositive pigs. The vaccination schedule s for SOWS and fattening pigs in view of the eradication of ADV are di scussed.