A mouse model of Pasteurella haemolytica infection and its use in assessment of the efficacy of P haemolytica vaccines.

A method for infecting mice with Pasteurella haemolytica is described. Mice were inoculated intraperitoneally with P haemolytica incorporated in gastric mucin, killed at various time intervals thereafter and viable counts of bacteria were performed on liver suspensions. P haemolytica grew at an exponential rate in the livers of normal mice. Mice vaccinated against P haemolytica A1 were protected against homologous challenge and viable counts decreased rapidly in their livers. Mice given trivalent P haemolytica vaccine (types A1, A2 and A6) were protected against challenge with P haemolytica types A1 and A6, but were not protected against challenge with types A2 and A9. These results correlate with findings in sheep.