[Vaccination in Aujeszky's disease on enzootic fattening farms].

An experiment was carried out on 125 pigs, originating from immune mothers on an enzootic for A. D. swine-breeding farm. The pigs were vaccinated once and twice with living vaccine MK-25 at different moments after their weaning. On the 180th after the vaccination the pigs were infected with a virulent (10(6) TCID) pseudorabies virus. They were studied clinically, serologically, virologically and pathomorphologically. It was proved that the vaccination of pigs, born by immune mothers, did not bring about the formation of a solid active immunity due to the neutralization of the vaccinal virus by the colostral immunity. A later vaccination of the pigs after the exhaustion of colostral immunity, did not lead to an increased vaccination effect, since during that period met with the persistent virus on the enzootic farm. Re-vaccination, however, created resistance of pigs to infection and a limited persistence of virulent virus.