An experimental infection with classical swine fever in E2 subunit marker-vaccine vaccinated and in non-vaccinated pigs

The clinical and virological protection induced by an E2 sub-unit marker-va ccine against Classical Swine Fever (CSF) was examined during an experiment al infection in vaccinated and non-vaccinated pigs. Forty-five pigs were eq ually distributed over three adjacent pens of an isolation unit, there was only indirect (airborne) contact between pigs in the different pens. In pen 3 all pigs were vaccinated twice with 4 weeks interval. Pigs in pens 1 and 2 were not vaccinated. Two weeks after booster vaccination, one randomly s elected pig in the middle pen was experimentally inoculated with CSF virus. After the initial virus spread in the infected pen, all pigs in the non-va ccinated adjacent pen were infected. In the vaccinated pen, seven out of 14 pigs became infected during the experiment. Survival analysis showed that virus transmission by direct and indirect contact was significantly (p < 0. 001) delayed in vaccinated pigs as compared to non-vaccinated pigs. In the non-vaccinated pens over 40% of the pigs died and typical clinical signs we re noticed. In the vaccinated pen no mortality and no clinical symptoms wer e observed. Although double vaccination with an E2 sub-unit marker-vaccine was able to prevent the clinical course of the disease it was unable to pre vent infection through indirect contact. This finding combined with the slo w serological response after vaccination will complicate the possible use o f the vaccine in emergency vaccination programmes. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.