Studies on comparative efficacy of Haemorrhagic septicaemia vaccines in buffalo calves

A total of eighty buffalo calves were immunized against HS vaccines. Alum precipitated HS vaccines and oil based HS vaccine procured from different sources were used. The immune status of animals was studied using indirect haemagglutination test (HIA) and mouse protection test. The sera of the animals were examined for HIA titres on day zero (before vaccination) and thereafter on 15th, 30th, 45th, 60th, 75th and 90th day post Vaccination. All the test gave zero titre on day 0. A very poor immune response (GMT 2.1, 4.3, 2.8 and 2.1 for vaccines of NIAB, VRI, HPL and SPV, respectively) was observed on 15th day post vaccination. Maximum HIA geometric mean titre alum precipitated vaccines of VRI, HPL and SPV GMT 64, 64 and 52, respectively were recorded on 45th day post vaccination. Thereafter a decline in the titre commenced and titre recorded on 90th day for VRI, HPL and SPV were GMT 22.6, 22.6 and 14.9, respectively. The sera of animal vaccinat ed with oil based HS vaccine of NIAB showed high antibody titer than alum precipitated HS vaccines. The increase in antibody titre was gradual up to 90th day post vaccination. The HIA GMT was 73.3 on 45th day post-vaccination but titre was increased up to 90.5 on 90th day post vaccination. The sera having HIA titre of 1:16 and above protected 100% of challenged mice. The sera having titre 1:8 protected 80% challenge mice, but the sera with HIA titre 1:4 conferred no protection to the passively immunized mice. Furthermore, control animals lost their lives in response to challenge inoculum as 100% mortality was recorded. A strong relationship between HIA titre and mouse protection test was found. The oil based HS vaccine give better and long lasting immunity up to a period of 90 days. The alum precipitated vaccines gave a dismal picture and necessitates attempt for its improvement and switching over to other vaccines which may give long lasting immunity.