Comparative efficacy of different vaccines against pasteurellosis in ducks

Abstract

Two isolates of Pasteurella mul tocida from ducks viz. DP1 and DP5 isolated from ailing/dead ducks from Kuttanad area and maintained in the virulent form were used separately for the preparation of different vaccines viz., bacterin, bacterin with oil adjuvant and sonicated antigen with oil adjuvant. The biological and biochemical characters of both the isolates were compared and are in confirmity with the characters described for the species by earlier workers. Both the isolates were pathogenic to ducks and mice as all the inoculated ducks and mice were killed with in 72 h. The LDso for the DP1 isolate in one month old ducklings and six month old ducks were determined to be 23 and 32 cells respectively whereas the LDso of DP5 isolate for one month old ducklings was determined to be 17 and for adult ducks LDso was 21 cells. Immunogenic potential of different vaccines prepared using DP1 and DP5 isolate were tested in ducks by giving two doses of vaccine. The first dose was given at four weeks of age and second dose was given 80 days after the first dose. The birds were challenged with 0.1 ml of culture containing 100 LDso of fully encapsulated virulent form of bacteria at 20 days interval till 80th day and then at 90th and 120th day after the first dose of vaccine. A higher percentage of protection was conferred by oil adjuvant vaccines prepared using DP1 and DP5 isolate and sonicated antigen with oil adjuvant prepared using DP1 isolate. The serum samples were collected from vaccinated birds at regular intervals of 0 I 7 I 20 I 40 I 60 I 80 I 90 and 120 for indirect haemagglutination test and the titres obtained were ranging from 8 to 256. More evaluation and elaborated field trials are required before advocating bacterin with oil adjuvant for field use.