Evaluating ability on growth, virulence and immune response of Riemerella anatipestifer bacteria isolated from septicaemia ducks in Viet Nam

Abstract

In this study, three strains of Riemerella anatipestifer (RA) isolated from septicemia ducks were selected for evaluating their ability of growing on artificial media, virulence as well as ability of inducing immune responses on the experimental ducks. The result of comparing the growth ability of these bacteria trains on 3 common media, such as: BHI, TSB and LB showed that all three strains of RA
grew well on BHI medium, reaching 10.9x109 CFU/ml. The virulence of the three tested RA strains in ducks was different, the lowest LD50 dose in 4-week-old ducklings was 48x106 and the highest was 360x106. All three RA strains were able to induce immune response in the experimental ducks. Antibody titer in the ducks after recieving two immnunity doses within 28 days reached around 9 to
11 log2 . Further more, 90-100% of the exprimental ducks after recieving two immnunity doses were protected when challenging duck with dose of 5LD50 of the RA strains/duck. The findings of this study is a scientific basic for selecting the potential RA bacteria strains serving for future research
on vaccine production.