Intensive regional vaccination with a gI-deleted vaccine markedly reduces pseudorabies virus infections

The development of marker vaccines against pseudorabies virus (PRV) and companion diagnostic tests have enabled us to perform a unique field trial. In this study, the effect of intensive regional vaccination on pig-finishing herd immunity was directly measured by comparing the seroprevalence of antibodies to glycoprotein I in trial and control groups. The seroprevalence of infected finishing herds in the trial region decreased from 81% at the start of the trial to 19% after 2 years (p < 0.001). The mean seroprevalence of infected pigs in these herds diminished from 49 to 5% (p < 0.001). In the control group, representing routine PRV control, no significant change in seroprevalences was noticed.