VACCINATION OF MATERNALLY IMMUNE PIGS WITH A LIVE AUJESZKEYS DISEASE VACCINE BY COARSE SPRAY AND OTHER ROUTES

33 ten weeks old passively immune weaners were inoculated with live, a ttenuated Aujeszky's disease (AD) vaccine, according to four different vaccination protocols: (groups A/A2) 3 X coarse spray vaccination at 10, 11 and 13 weeks of age, (groups B/B2) 1 X coarse spray at 10 weeks of age followed by 1 X intramuscularly at 13 weeks, (C) 1 x intranasa l instillation at 10 weeks of age, and (groups D/D2) 2 X intramuscular ly at 10 and 13 weeks of age. A further 10 weaners were included as un vaccinated controls (E/E2). Spray vaccination was technically simple t o perform but on average, 20% of subjects were reluctant to expose the mselves to the spray. Clinical reactions were absent apart from mild f ever in one pig from group B. Weight gains between 10 and 17 weeks of age were slightly lower in group A and group B weaners, compared to co ntrol unvaccinated pigs and pigs vaccinated by other routes. Virus neu tralising (VN) antibody response was extremely uneven between individu als in groups A and B. Group D pigs vaccinated 2 X intramuscularly sho wed a 3 week lag in developing high levels of antibody but the intramu scular route, as well vaccination by intranasal instillation, proved t o be the most dependable technique for inducing uniformly high levels of VN antibody. Challenge with virulent ADV at 17 weeks of age resulte d in death from Aujeszky's disease of all five control pigs. One pig i n group A which had no VN antibody, also died. All other pigs were pro tected against death. Surviving pigs in group A were marginally better protected against clinical disease compared to other pigs vaccinated by other routes, notably those in group D. Otherwise, there were no si gnificant differences in the severity or duration of clinical illness between pigs vaccinated by different routes. Challenge at 26 weeks of age resulted in severe illness in control pigs and all died or were eu thanased. All vaccinated pigs survived. Protection against clinical il lness and growth arrest was maximal in pigs vaccinated 3 X by coarse s pray (group A2). An average 0.6 days of fever, 0.4 days of inappetance and 0.4 days of growth arrest were observed. Group B2 pigs vaccinated 1 X by coarse spray and 1 X intramuscularly had 3.8 days of fever, 4. 0 days of inappetance and 6.4 days of growth arrest. Group D2 pigs vac cinated 2 X intramuscularly showed 3.7 days of fever, 5.3 days of inap petance and 5.7 days of growth arrest. An intranasally vaccinated grou p was not included for challenge at 26 weeks.