A bread‐based lyophilized C‐strain CSF virus vaccine as an oral vaccine in pigs

A live attenuated cereal‐based classical swine fever (CSF) vaccine for oral application, a form of vaccine that farmers can use themselves, demonstrated the improvement of CSF control in backyard production systems in endemic areas. Due to the dependency on very low storage temperature (−20°C) of the cereal‐based oral CSF vaccine, a lyophilized cereal‐based oral vaccine has been developed and tested. Although some studies showed total protection against a virulent virus strain, the production procedure is still considered complex. In this study, the lyophilized oral CSF virus, which is easy to produce and could be kept in the form of a bread‐based vaccine at 4°C for an extended time, was tested for the ability to induce a humoral immune response in pigs. Among the materials tested as a base for the CSF virus vaccine, plain sliced bread was considered the most appropriate base because of its absorbing ability and virus titre maintenance. Titres of bread‐based lyophilized CSF virus vaccine were stable at around 3.67 log₁₀ TCID₅₀ per ml for 7 months at 4°C. Pigs aged 5 and 8 weeks that orally received five bread‐based lyophilized CSF virus vaccine showed seroconversion of over 90% at 14 dpv. At 28 dpv, both age groups showed 100% seroconversion. In conclusion, the bread‐based lyophilized CSF virus vaccine can be an alternative choice for oral vaccination of pigs. Due to the simple process of production and the need for less virus titre, vaccine prices could be lowered. However, vaccine thermostability has to be improved to allow the vaccine delivery to be less dependent on functioning cool chains.