Field study of Streptococcosis / Lactococosis and Yersiniosis vaccine effectiveness in immunogenicity and survival rate of rainbow trout (Oncorhynchus mykiss)

In this study,the immunogenicity of streptococcosis/lactococcosis and yersiniosis vaccine in rainbow trout was investigated in farm.900 fish with an average of 50±5 g were divided into three treatments and three replications (injection treatment, immersion treatment and control group).Fish were kept for 60 days and samples were taken on the 30th and 60th days.Then the fishes were challenged for 14 days with three bacteria, Streptococcus iniae, Lactococcus garvieae, and Yersinia ruckeri.Sampling was done to evaluate lysozyme activity,complement, antibody titer and survival rate. The results indicated a significant increase in serum complement and lysozyme activity on the 30th and 60th days of sampling in the vaccinated groups compared to the control group (P<0.05).Antibody titers against S. iniae, L. garvieae and Y. ruckeri on the 30th and 60th days of sampling in the vaccinated groups had a significant increase compared to the control group (P < 0.05).The  relative percentage survival after 14 days of challenge with S. iniae, L. garvieae and Y. ruckeri in the injected group was (70, 60, and 76.6%),respectively, which was significant compared to the control group (P<0.05).Also, the relative percentage survival in the immersion group with S. iniae, L. garvieae and Y. ruckeri was(30, 36.6 and 53.3%),respectively, which was significant only in the group immersed with S. iniae (P<0.05).In general,it can be concluded that the use of polyvalent vaccine by injection and immersion has significant effects on the immunity and survival rate of rainbow trout. However, the injection method is more effective and suitable than the immersion method.