Assessment of safety and protective value of a cell culture modified strain "C" vaccine of hog cholera/classical swine fever virus.

The protective value of a commercial strain "C" vaccine of classical swine fever (CSF) was tested in weaner pigs. Vaccinated animals were challenged intranasally with the virulent hog cholera virus (HCV) strain ALFORT/187 in groups of four pigs each at one to four weeks post vaccination, respectively. Non-vaccinated control animals were challenged in the same manner. Some vaccinated pigs seroconverted as early as one week post vaccination with all pigs yielding neutralizing antibodies (nAb) against the vaccine virus at two weeks post vaccination. After challenge no clinical signs were observed in any of the vaccinated animals whereas non-vaccinated control animals developed fever starting in general on the fourth day post challenge. In vaccinated pigs no challenge virus could be isolated from leucocyte samples taken on days 3 to 7 post challenge while HCV was isolated from buffy coat leucocytes of all non-vaccinated animals. Six out of eight control animals were sacrificed and viral antigen was detected in tonsils, mandibular lymph node and spleen in four animals, exclusively in tonsils in one animal and none in another animal. Two non-vaccinated animals that survived the experiment seroconverted after challenge and developed nAb against the HCV strain ALFORT/187.