VIRULENCE STUDIES OF PASTEURELLA MULTOCIDA IN MICE, DUCKLINGS AND ADULT DUCKS

Pasteurella multocida is a Gram negative bacterium causing severe disease in a multitude of hosts; the A: 1 strain of this bacterium is extremely virulent to hosts. In this study, the virulence of P. multocida A: 1 strain was assessed in one month old ducklings, six months old ducks and eight weeks old albino mice. The groups of experimental animals were inoculated with the different dilutions of the bacteria through subcutaneous route. The control groups were sham inoculated with sterile phosphate buffered saline via respective routes. Mortality was recorded for two weeks post inoculation. All the dead animals and birds were examined for specific gross lesions of pasteurellosis and attempted re-isolation of the organism on blood agar from their internal organs. The median lethal dose was calculated using Reed and Muench method. For ducklings, the median lethal dose was 13 colony forming units and the dilution giving 50 % end point with 0.1 ml subcutaneous dose was 10-7.4. The median lethal dose could not be arrived at for mice and adult ducks as the strain killed all the inoculated mice even in the lowest dilution tested, while most of the adult ducks were resistant to infection.