Abstract

Bacterial diseases remain a major constraint to intensive rabbit production, with pasteurellosis representing a leading cause of mortality and substantial economic losses. In addition to Pasteurella multocida, members of the family Enterobacteriaceae, particularly Escherichia coli, are frequently associated with fatal infections in rabbits. In the present study, a locally formulated, combination inactivated vaccine containing E. coli and P. multocida adjuvanted with Montanide ISA 70, was developed and its immunogenicity and protective efficacy were evaluated in rabbits. A total of 370 rabbits were divided into 4 experimental groups: polyvalent inactivated P. multocida vaccine, polyvalent inactivated E. coli vaccine, combination inactivated P. multocida and E. coli vaccine, and unvaccinated controls. All vaccinated rabbits received two subcutaneous doses (0.5 ml) administered one month apart. Three weeks after the booster dose, animals were challenged with virulent strains of P. multocida or E. coli. Vaccine-induced humoral immune responses were assessed using indirect hemagglutination and enzyme-linked immunosorbent assay. The protective effectiveness was assessed by challenge trials and determination of LD₅₀. Combined inactivated vaccine elicited the highest antibody responses and conferred up to 90% protection against challenge with virulent P. multocida serotypes A and D and E. coli serotypes O157, O151, and O125. In comparison, monovalent vaccines induced lower levels of protection. These findings demonstrate that the combination inactivated P. multocida and E. coli vaccine is immunogenic and effective, supporting its potential application for controlling pasteurellosis and colibacillosis in rabbit production systems.

Key words: Rabbit protection, P. multocida, E. coli, Challenge test, Vaccine, ELISA.