Vol. 9, Issue 10, Part J (2025)

Outer Membrane Vesicle (OMV) and bacterin were extracted from the most pathogenic porcine isolate of Pasteurella multocida capsular type A selected on the basis of pathogenicity trial in mice and vaccines prepared from the extracts were immunized in pigs. The comparative immunogenicity of the two vaccine preparations of Pasteurella multocida was determined by monitoring the corresponding serum antibody titres at different time intervals 0, 7, 21, 30, 45, 60, 75, 90 days post vaccination by indirect ELISA. The OMV extract vaccinated pigs showed a sharp increase in the ELISA antibody titre from the very first week (3.60±0.21) of immunization, reaching peak titre on the 60^th day post vaccination (6.40±0.19) and started to decline on 90^th day post vaccination. The pigs immunized with bacterin of the same strain of Pasteurella multocida showed serum antibody titre 3.20±0.34 on 7^th day post-immunization, reaching peak titre on the 28^th day (6.10±0.14) post-vaccination, thereby gradual decrease in the mean serum antibody titre (5.9±0.25) from the 60^th day, till 90^th day (5.70±0.23) post immunization. In both the vaccine preparations, the antibody titre showed gradual decreases up to 90^th day post vaccination. The statistical analysis revealed no significant difference between the two vaccine preparations (OMVs and bacterin) based on mean serum antibody titre at different days post-immunization. The result of passive mouse protection test revealed that the 21^st and 28^th day post vaccination serum sample (OMV vaccine) and 28^th day serum sample (bacterin vaccine) produced (100%) protection in mice.