Bovine pneumonic pasteurellosis: effect of vaccination with live Pasteurella species.

Experimental bovine pneumonic pasteurellosis was induced in beef calves by a transthoracic challenge exposure with Pasteurella haemolytica serotype 1 or P multocida type 3. Challenge exposure lesions were quantified by a lesion scoring system based on size and extension of lesions with larger scores assigned to the more severe lesions. Calves inoculated with live Pasteurella sp by aerosol or parenteral routes developed high serum antibody titers to the homologous organism, as determined by a quantitative fluorometric procedure. Mean lesion scores were approximately 2 to 20 times higher in control than those in vaccinated calves. There was a significant correlation (P less than 0.05) between high serum antibody titers at the time of challenge exposure and a low lesion score in 4 of 6 experiments.