Survey on Immunogenicity and protective efficacy of Yersinia ruckeri lipopolysaccharide (LPS) against yersiniosis disease in Rainbow trout (Oncorhyncus mykiss)

Regarding the importance of yersiniosis in the country and the necessity of vaccination of fish, in this study, the effects of Yersinia ruckeri lipopolysaccharide on the efficacy and immunity of Yersinia ruckeri bacterin were evaluate. 480 pieces of fish (7±1.2 g) were randomly divided into 8 equal groups, each group was divided into three replicates (20 fish/ replicate). Group A, B and C were fed with LPS (300μg/kg/Bw), LPS+bacterin (109 cfu/g) and bacterin respectively in the first and third weeks of the study. In the immersion group (D), the fish were immersed in the bacterial suspension (109 cfu/ml) for 2 minutes at 0 and 14 days. The injection groups (E, F and G) were immunized by intraperitoneal route with (1010 cfu/ml), LPS (300 μg /ml) and bacterin+LPS respectively, and on days 0, 30 and 60 blood and serum samples were prepared then blood and immune parameters were compared between immunized fish. The results showed that injection of bacterin+LPS significantly improved the stimulation of nonspecific and specific immunity factors in most groups (p < 0.05) The efficacy of bacterin +LPS in the oral treatment was similar to immersion immunization and was significantly lower than the injection method (p < 0.05). The results of the current study showed that adding LPS to bacterin, in addition to improving the efficacy of the vaccine by injection and oral administration, also increased their immunization. Therefore, after supplementary studies, it can be used as an appropriate and economical candidate for the preparation of the economical vaccine in trout.