Classical Swine Fever: Active Immunisation of Piglets with Subunit (E2) Vaccine in the Presence of Different Levels of Colostral Immunity (China Strain)

The aim of this study was to investigate the efficacy of the subunit vaccine against virulent CSF infection in piglets deriving from sows vaccinated with China strain. The experimental research included 34 piglets aged 45 days (13 naïve and 21 piglets originating from sows immunized with China strain CSFV). Three experimental groups consisting of seven animals each were formed based on serological examination of piglets aged 40 days. At the age of 45 days, the piglets were vaccinated with a subunit vaccine. After revaccination, the piglets were challenged with a virulent CSFV strain. With the aim of controlling virus shedding, two susceptible piglets were introduced into each group. After challenge, clinical monitoring of animals was performed, and blood samples were obtained to detect viremia and the presence of antibodies against CSF. The control of CSFV shedding by vaccinated, artificially infected piglets was performed by RT-PCR analysis of oropharyngeal and rectal swabs. After death or sacrifice of the animals, autopsy was performed along with the gross pathological examination and tissue sampling with the purpose of determining the presence and distribution of CSFV (ELISA and RT-PCR). Application of the subunit vaccine in piglets originating from sows vaccinated with China-strain resulted in a good active immune response. Following challenge virus shedding was confirmed, but without contact infection in susceptible animals in cohabitation. The results indicate that the subunit vaccine may have a potential application in the control of CSF in enzootic regions.