Oral immunization of pigs against classical swine fever. Course of the disease and virus transmission after simultaneous vaccination and infection

The efficacy of simultaneous vaccination of pigs against classical swine fe ver (CSF) and challenge was evaluated. In this study, domestic weanling pig s were vaccinated orally with a conventional live virus vaccine based on CS F virus (CSFV) C strain and were challenged simultaneously with CSFV of dif ferent virulence. All the animals vaccinated and challenged with a high dos e of highly virulent Koslov strain died while three of five animals challen ged with a low dose of highly virulent Alfort 187 strain survived shed the virus in nasal secretions, developed antibodies, and four of them showed a transient viremia. All the animals vaccinated and challenged with the low v irulent field isolate MV 140/Riems survived showed a short viremia and deve loped antibodies. No CSFV or CSFV RNA could be detected in the animals surv iving the infection. This study demonstrates that oral vaccination of wild boars in an infected area bears no risk for the development of a Persistent CSF infection.