Vaccination of cattle against pseudorabies (Aujeszky's disease) with homologous virus (herpes suis) and heterologous virus (herpes bovis 1).

Study was made to determine whether vaccination of cattle against pseudorabies (PR; Aujeszky's disease) affords protection upon subsequent intranasal challenge exposure with virulent virus. Vaccinations were performed with a commercially available oil-adjuvant PR virus vaccine, in some cases supplemented with A1(OH)3 (given subcutaneously), with the attenuated NIA4 strain of PR virus (given intranasally), and with a commercially available temperature-sensitive mutant of bovine herpesvirus-1 (infectious bovine rhinotracheitis [IBR] virus) given intranasally. Challenge exposure was performed intranasally with 10(3) median lethal doses (LD50) of the virulent PR virus. In earlier experiments, it was found that LD50 median tissue culture infective doses of this virulent PR virus in primary pig kidney cells represented about 1 LD50 for cattle. This LD50 was practically no different for cattle whether or not they had antibodies against PR virus before exposure to virulent PR virus. In the seropositive animals, antibodies were present presumably as a consequence of a previous IBR infection in the field. Vaccination intranasally with NIA4 or IBR virus did not result in serologic response or protection against challenge exposure. The inactivated-virus vaccine induced a good serologic reaction, but there was poor protection against challenge exposure. Consequently, vaccination of cattle at risk of exposure to virulent PR virus cannot be advised. In the present experiments, initiation of infection with virulent PR virus in cattle always resulted in disease and death.