Oral immunisation of wild boar against classical swine fever: uptake studies of new baits and investigations on the stability of lyophilised C-strain vaccine

The aim of this study was to investigate the uptake of new spherical and cuboid baits by wild boar and domestic pigs and to evaluate the stability of lyophilised C-strain vaccine stored at different environmental temperatures. New baits were designed to improve the consumption of the vaccine against classical swine fever by young wild boar. Our uptake studies showed that neither wild boar nor domestic pigs at the age of 2 months picked up the baits at all. Although the animals began to pick up the baits incompletely at the age of 3 months, a complete uptake of both the new baits and the older ones was only observed from the age of 4 (domestic pigs) and 4.5 (wild boar) months on. Nevertheless, the larger spherical baits with a diameter of 3 cm were taken up more effectively than the recent vaccine baits. As expected, lyophilised vaccine showed a higher stability than liquid vaccine, especially at temperatures ≥24°C. Independently of the stabiliser (GS4 or TSM) used, there are no differences between the virus titres detected within a storage period of 7 days. As the lyophilised C-strain vaccine was more stable at higher temperatures than the liquid vaccine formulation, we recommend to use lyophilised vaccine for oral immunisation of wild boar in the future, as oral vaccination is also carried out in the summertime.