Evaluation of immunogenicity of bivalent vaccine streptococosis / Lactococcosis in rainbow trout (oncorhynchus mykiss)

In this study the Hemato- immunological responses of rainbow trout (Oncorhynchus mykiss) to vaccination with bivalent lactococcal/streptococcal vaccine were investigated. Two hundred and forty rainbow trout fingerlings (Weighing 30±1.7) were randomly divided into two equal groups in triplicates. Fish in vaccinated treatment intraperitonealy injected with vaccine on day zero and booster vaccine were directed by immersion route on day 30th of study. The control group was injected with sterile PBS, identical to vaccinated group. Blood and head kidney samples were collected from vaccinated and non-vaccinated groups at days 0, 14. 30, 45 and 60 of study. Hematological parameters including: hematocrit, hemoglobin levels, red blood cell count and White blood cell count as well as immunological parameters (Lysosim and complement activity, phagocytosis rate of head kidney macrophages) were investigated and compared among the groups. Results showed that no differences were observed in hematological parameters (P>0.05) except the number of white blood cell count which significant increase in in vaccinated group were seen compared with the control group. All evaluated immunological parameters of vaccinated group were significantly higher in vaccinated group (p < 0.05). It can be concluded that vaccination of rainbow trout by bivalent vaccine against streptococcus/lactococcus disease can stimulate immune response of fish until 60 days post immunization without any side effect on hematological parameters. Then this procedure of vaccination seems suitable for rainbow trout.