Immunogenicity of a classical swine fever bait vaccine (Flc-LOM- BErns) in hybrid-wild boars

To identify the best method of distributing vaccine baits for animals, the oral vaccine Flc-LOM-BE^rns was buried or placed directly on the ground within a mountainous area measuring 163 ha. Wild boars were observed more often around sites where the oral vaccine was buried than around sites where the oral vaccine was placed directly on the ground. Only wild boars consumed both the bait and the vaccine formulation. To confirm whether the Flc-LOM-BE^rns vaccine strain has DIVA function, it was spread or buried within a mountainous area of 2.3 ha that was frequented by grazing hybrid-wild boars. Among the 15 hybrid-wild boars captured before consuming the oral vaccine, two were positive for anti-CSFV E2, but negative for anti-BVDV E^rns antibodies. The CSFV E2 and BVDV E^rns antibody positivity rates in 46 hybrid-wild boars captured 6 weeks after distributing the oral vaccine were 56.5 % (26/46, 95 % CI: 42.2–69.7) and 52.1 % (24/46, 95 % CI: 38.1–65.8), respectively. However, the CSFV E2 and BVDV E^rns antibody positivity rates at 28 weeks post-distribution of the oral vaccine decreased by 10.3 % and 13.7 %, respectively, when compared with those in hybrid-wild boars captured after 6 weeks. Since the antibody positivity rates induced by the oral vaccine decreased after 7 months, it is necessary to distribute the oral vaccine at least twice a year (early spring and late fall).