The effect of bivalent vaccine, streptococcus/ yersinios on some of the blood and Immunologic factors in rainbow trout, Oncorhynchus mykiss

Streptococcosis and Yersiniosis are important diseases for the aquaculture industry especially in rainbow trout (Oncorhynchus mykiss) in our country. The aim of this study was to investigate the effects of a bivalent vaccine (Streptococcus iniae and Yersinia rockeri) on the immune responses including serum lysozyme, complement activation, bactericidal, respiratory burst (NBT), total protein, albumin, globulin and some haematological indices in rainbow trout.In this study three hundred rainbow trout fingerlings (۲۵±۲g) were randomly divided into four equal groups, each in triplicates. The groups were as follow: Streptococcosis vaccine, Yersiniosis vaccine, bivalent vaccine and control group. Fish in vaccinated treatment intraperitoneally injected with ۱۰۰ microliter vaccine on the first day. The control group was injected with sterile PBS, identical to vaccinated group. Blood samples were collected from vaccinated and non-vaccinated groups at days ۰, ۳۰, and ۶۰ of study. The results demonstrated that lysozyme rate in bivalent vaccine were significantly higher at day ۶۰ post-immunization compared to the control group (p<۰.۰۵). A significant increase was observed in the complement activation in bivalent vaccine at day ۳۰ and ۶۰ post-vaccination compared to the other groups (p<۰.۰۵). Also, these results demonstrated that number of WBC in vaccinated groups were higher than control treatment. Generally, it can be concluded that the administration of bivalent Streptococosis/Yersiniosis vaccine to the rainbow salmon provided appropriate protection against disease and effectively induced the immune response against these two diseases which is comparable to either of the vaccines separately. Therefore, investigation of the efficiency of the bivalent vaccine at commercial level is highly warranted.

Keywords:

Bivalent vaccine , Streptococosis , Yersiniosis , Blood and Immune indices