To evaluate the safety and immunogenicity of combined hemorrhagic septicemia (HS) and blackleg (BL) vaccine, combined vaccine was produced in two different formulations (group one, G1 and group two, G2) and compared with safety and immunogenicity of monovalent Hs and BL vaccines in different doses. G1 combined vaccine was vaccinated in 4 and 2 ml in to five calves each while G2 combined vaccine, the monovalent HS and blackleg vaccines were vaccinated in 2 and 1 ml amount into to five calves each leaving ten non-vaccinated calves managed similarly as vaccinated ones. The safety test was made by giving single and double doses of experimental vaccines and double doses of monovalent vaccines in each case using two calves per dose group. The immunogenicity of BL vaccine component in the combined vaccine was evaluated by using 10 guinea pigs per group for six different doses of combined and monovalent blackleg vaccine, leaving 10 non-vaccinated controls. The study indicated that the protection against virulent challenges for animals vaccinated with G1 combined vaccine at 2 ml, G2 vaccine at 1 ml, monovalent HS and BL vaccine vaccinated at 1 ml doses was by far less than 90%. On the other hand, protection against experimental challenge for G1 vaccine vaccinated in 4 ml amount was 100% against both HS and blackleg virulent challenges while the protection against experimental challenge for G2 vaccine vaccinated in 2 ml amount was 66.67% against the HS virulent challenge and 90% against BL virulent challenge. So G1 combined vaccine vaccinated in 4 ml was found to be the best candidate vaccine according to this experiment which needs to be confirmed at field test before use for mass vaccination.
Key words: Combined, hemorrhagic septicemia, blackleg, safety, immunogenicity.