Comparison of Intranasal and Parenteral Vaccination Against Aujeszky’s Disease in 12-Week-Old Pigs from Immunised Dams
A pilot experiment in groups of five 10-week-old seronegative pigs showed that intranasal (i.n.) vaccination with Bartha’s K strain of Aujeszky’s disease (AD) virus induced a good antibody response and resulted in nearly complete protection against disease following severe i.n. challenge two months post-vaccination (p.v.). In addition, excretion of challenge virus was much reduced as compared to that of controls. There was little difference in these respects between pigs vaccinated with 104, 106 or 108 plaque forming units. No untoward reactions following i.n. vaccination were observed.
The main experiment was done with 12-week-old pigs from dams revaccinated shortly before parturition. All pigs had maternal antibodies detectable in a sensitive neutralisation test. They were randomly distributed in three groups of ten and one of nine. One group was vaccinated intranasally with 106 TCID50 of the Bartha strain, two groups parenterally with a commercially available modified live virus vaccine based on the same strain and one group was left unvaccinated. After three weeks one of the parenterally vaccinated groups was revaccinated.
Intramuscular (i.m.) vaccination had a slow but distinct serologic effect; a second i.m. vaccination after three weeks resulted in a booster response. I.n. vaccination gave a faster serologic effect than i.m. vaccination while titres continued to increase over a long period.
Six pigs of each group were challenged after 6 weeks and four pigs after 4 months, together with four or five unvaccinated controls.
At 6 week p.v., one of the control pigs died after challenged and the other showed a mean growth arrest period of 12 days, reflecting severe clinical disease. No vaccinated pigs died. The animals vaccinated once intramuscularly were less severely affected than the controls, the mean growth arrest period being 6.5 days. Pigs vaccinated intranasally or twice intramuscularly were very well protected and on an average did not lose weight.
At 4 months p.v., all pigs survived the challenge, but clinical disease of varying severity developed in all groups. Intranasally vaccinated pigs were markedly better protected than pigs vaccinated twice intramuscularly, despite the fact that the latter had somewhat higher serum antibody titres. The mean growth arrest periods of the different groups were more than 19 days for the controls, 13.5 and 12 days for pigs vaccinated intramuscularly once or twice and 6.5 days for intranasally vaccinated pigs.
Particularly after challenge at 6 weeks p.v., the intranasally vaccinated pigs excreted much less virus than the parenterally vaccinated pigs. In this respect there was little difference between pigs vaccinated intramuscularly once or twice, but both categories excreted less virus than the controls. A similar pattern, though less marked, was observed after challenge at 4 months p.v.
It is concluded that i.n. vaccination of pigs against AD is promising enough to warrant further study, particularly as a means to overcome interference of maternal antibodies with active immunisation.
KeywordsDepression Titration Rhinitis Sera ECSC
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