STUDY ON SOME IMMUNOLOGICAL RESPONSES OF RAINBOW TROUT (ONCHORHYNCHUS MYKISS) TO SOME ANTIGENS OF STREPTOCOCCUS INIAE

Some specific and non-specific immune variables of rainbow trout were assessed following vaccination of fish with formalin killed cells (FKC) and FKC containing extra cellular products (ECP) of S. iniae. Rainbow trout weighing 80-100 g were vaccinated by intraperitoneal (i.p), dip and oral routes using FKC and FKC plus ECP with or without Fround adjuvant (FA) at 16-17°C.Antibody titration, lysozyme activity, serum bacterial killing activity and population of immunocompetent cells were measured on 3, 6, 9, 12, 15 and 18 weeks postvaccination. Data were analyzed by ANOVA. Results showed that the highest antibody titers were produced in i.p vaccinated fish with FKC plus ECP and immunized fish with FKC by dip, respectively. However, oral administration resulted in the lowest response. Also, the level of antibody production was higher during initial period of post-immunization, while it reduced to lower levels at the end of sampling time. Similar results were obtained when lysozyme activity and bacterial killing capacity of sera samples were estimated. Moreover, while,leukocyte and lymphocyte populations in immunized fish were generally higher than control groups, heterophil and monocyte counts were varied during the sampling periods.Reuslts show that both humeral and cellular immunities of trout are enhanced following immunization of fish with FKC with or without ECP administered as i.p and dip.However, i.p administration of FKC with or without ECP could cause higher response than both dip and oral routes.