1Department of Microbiology, Faculty of Veterinary Medicine, University of Urmia, Urmia, Iran
2Department of Aerobic Vaccine Production, Razi Vaccine and Serum Research Institute, Karadj, Iran
3Department of Biotechnology, Razi Vaccine and Serum Research Institute, Karadj, Iran
Haemorrhagic septicaemia (HS) is a fatal systemic disease of cattle and buffaloes. Some control is achieved with administration of alum-precipitated or oil-adjuvanted killed whole-cell vaccines injected subcutaneously. These vaccines, however, provide only short-term immunity and for effective use, they should be administered annually. We constructed an aroA attenuated derivative of a Pasteurella 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.