PROTECTION AGAINST HEMORRHAGIC SEPTICEMIA INDUCED BY VACCINATION OF BUFFALO CALVES WITH AN IMPROVED OIL ADJUVANT VACCINE

An experimental oil adjuvant vaccine was developed against haemorrhagi c septicaemia, a disease of cattle and buffalo caused by Pasteurella m ultocida serotype B and E. Mineral oil, Mercol 52, was used as adjuvan t together with Span 85 and Tween 85 as emulsifiers. The vaccine was e valuated by single dose intramuscular immunisation of 1-2 year old buf falo calves. IgG and IgM class antibodies were determined by ELISA. Th e group of animals immunised with the experimental oil adjuvant vaccin e showed a high titre of the IgG class of antibodies measured at 300 d ays post vaccination. To compare the protective efficacy of the vaccin e with the commonly used broth bacterin, another group of buffalo calv es was immunised by broth bacterin. This group showed a low level of I gG antibodies. Protection was assessed by challenge with 10(9) viable bacteria of P. multocida type B:2,5 administered subcutaneously, 250 d ays post vaccination. Animals vaccinated with the experimental oil adj uvant vaccine were fully protected. The other groups of animals, vacci nated with broth bacterin or used as control (non-vaccinated), develop ed 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 adjuva nt vaccine was superior to broth bacterin in providing protection agai nst experimental haemorrhagic septicaemia in young buffalo calves beyo nd 250 days.