Serological evaluation of Pasteurella multocida antigens associated with protection in buffalo calves.

Different antigens of Pasteurella multocida Carter's type 6:B including whole bacterium, antigen heated at 56 degrees C, antigen heated at 100 degrees C, sonicated antigen, capsular antigen, potassium thiocyanate extract, lipopolysaccharide and sodium salicylate extract were evaluated to assess protection in buffalo calves against haemorrhagic septicaemia. Sera from calves with known protection status in experimental challenge were titrated by enzyme-linked immunosorbent assay (ELISA) against all antigens. Capsular antigen extracted with 2.5% sodium chloride was superior to other antigens for assessing protection status of buffalo calves against P. multocida by ELISA. This capsular antigen was able to differentiate clearly between well-protected, protected and unprotected animals.