Protection against haemorrhagic septicaemia induced by vaccination of buffalo calves with an improved oil adjuvant vaccine.

An experimental oil adjuvant vaccine was developed against haemorrhagic septicaemia, a disease of cattle and buffalo caused by Pasteurella multocida serotype B and E. Mineral oil, Mercol 52, was used as adjuvant together with Span 85 and Tween 85 as emulsifiers. The vaccine was evaluated by single dose intramuscular immunisation of 1-2 year old buffalo calves. IgG and IgM class antibodies were determined by ELISA. The group of animals immunised with the experimental oil adjuvant vaccine showed a high titre of the IgG class of antibodies measured at 300 days post vaccination. To compare the protective efficacy of the vaccine with the commonly used broth bacterin, another group of buffalo calves was immunised by broth bacterin. This group showed a low level of IgG antibodies. Protection was assessed by challenge with 10(9) viable bacteria of P. multocida type B:2,5 administered subcutaneously, 250 days post vaccination. Animals vaccinated with the experimental oil adjuvant vaccine were fully protected. The other groups of animals, vaccinated with broth bacterin or used as control (non-vaccinated), developed symptoms of haemorrhagic septicaemia. A strong relationship between IgG but not IgM class antibody level and resistance to challenge was observed. The experiment demonstrated that the experimental oil adjuvant vaccine was superior to broth bacterin in providing protection against experimental haemorrhagic septicaemia in young buffalo calves beyond 250 days.