Introduction: Hemorrhagic septicemia (H.S) is an acute septicemicdisease principally affecting cattle and buffaloes caused by Pasteurella multocida (P.multocida).The disease is highly fatal in nature and recovery is rare after onset of the clinical signs. The disease therefore,is controlled by mass vaccination in the countries, where it is endemic.Alum precipitated vaccine is one of the most important killed vaccine against the H.S which is widely used in the field condition of Punjab.
Material and Methods: Serial dilution of virulent bacteria was injected in to mice which were immunized with H.S Alum PrecipitatedVaccine. Ratio of survived and dead was calculated by Spearman Karber method and the protective index (P.I) value of Alum Precipitated H.S vaccine manufactured at Punjab Veterinary Vaccine Institute was calculated.
Results: The immunological study revealed that vaccine prepared at PVVI showed greater immunopotency. Around 100 mice free from pasteurella infection were used to evaluate the potency of Alum Precipitated H.S vaccine. The nutrient broth culture of H.S was used to induce infection. The 0.2 ml of broth dilution from 10−1to 10−10was used, as dilution increases death rate decreases in immunized mice.It indicate the minimum load of bacterium is required to induced infection and the vaccine inoculated in the mice protects them against the challenge with virulent P. multocida.
Conclusions: Difference of log units between vaccinated and unvaccinated mice was 4.2 Dilutions of 10−1, 10−3and 10−4were shown 100%, 60%, and 20% mortality in vaccinated groups respectively. 100% mortality was shown in control groups except dilutions of 10−6, 10−7(60%) and 10−8(40%). According to this method a difference of at least 4 log units between the LD50 of vaccinated and unvaccinated mice is essential as the potency requirements of the vaccine (De Alwis 1992). In the present study, the alum precipitated H.S vaccine produced a difference of 4.2 log units between the immunized and control groups of mice, which is clearly above the minimum requirement for potency of the vaccine.
Keywords: Hemorrhagic septicemia (H.S), Pasteurella multocida, Alum precipitated H.S vaccine, Protective index, LD50, Mice