Evaluation of pathogenicity and immunogenicity of native and mutant strains of Pasteurella multocida causative agents of Haemorrhagic septicaemia

Hemorrhagic septicemia (HS) is a fatal systemic disease of cattle and buffaloes. Some control is achieved with alum precipitated or oil-adjuvanted killed whole-cell vaccines injected subcutaneously, but these vaccines provide only short-term immunity and require annual administration for effective use. We constructed an aroA attenuated derivative of a P. multocida serotype B:2 strain by allelic exchange of the native aroA sequence with aroA sequences disrupted with a kanamycin resistance cassette. This strain was confirmed to be aroA mutant by PCR. The aroA derivative was highly attenuated for virulence in a mouse model of HS and rabbits. Mouse and rabbit challenge experiments showed that i.p. or i.m. vaccination of an aroA strain completely protected mice or rabbits against challenge with a high dose (>1000 LD50) of the parent strain.

Keywords:

P. multocida , live vaccine , aroA mutant , Hemorrhagic septicemia