INFLUENCE OF THE VACCINATION REGIME ON THE HERD IMMUNE-RESPONSE FOR SWINE FEVER

Surveys in three areas with emergency vaccination programmes revealed that 86-94% of the pigs vaccinated in the initial mass campaign had developed an adequate antibody titre against swine fever as compared with 29-55% of the pigs involved in supplementary vaccination campaigns. The serological response of piglets born from immunized sows rose with the age of vaccination from 11% at 5-6 weeks to 42% at 7-8 weeks and 77% at 9-10 weeks. In piglets born from immunized sows, a 50% ''take'' of the vaccine was not obtained before the age of 8-9 weeks. Re-vaccination of gilts born from immunized dams improved the immune status to almost the level observed after mass campaigns. To strengthen herd immunity in vaccination areas, the age of supplementary vaccination has been raised to 7-9 weeks, while breeding gilts are re-vaccinated when 6-7 months old.