Soluble anbgens from Renibactenum salmoninarum (Rs) incorporated Into ~rnmunostimu-lating complexes (iscoms) induced polyclonal antibod~es directed to the heat-stable, 57 kDa antlgen complex of Rs The antibodies were used in an enzyme-linhed immunosorbent assay (ELISA) for the detection of Rs antigens in salnlonid h d n e y sanlples The negative-positlve threshold value in the ELlSA was determined to be 0 10 based on the analyses of 408 samples from rainbow trout Oncorhynchus myklss, Arctic char Salvehnus alpinus, Baltic salmon Salmo salar, and brown trout Salmo trutta, all n e g a t~v e for Rs by bacterial culture The Rs organism was ~solated on select~ve kidney d~s e a s e medium (SKDM) after up to 12 wk of incubation from 45% of the samples collected from fish farms having enzootic bacterial h d n e y disease (BKD), and f~o m fish in populat~ons with clin~cal slgns of BKD ( n = 260) Soluble antigens of Rs were detected with the polyclonal ELISA In 50 % of these samples In a comparative evaluat~on of 3 d~agnostic techniques (bacterial culture, the polyclonal ELISA descnbed here, and a commerc~ally available ELISA based on monoclonal antibodies). 167 k~d n e y samples were individually analyzed The results of the d~agnostic tests (pos~tive or negative) were ~dentical for 95% of the examined samples A higher sensitivity of the polyclonal ELISA when compared with the monoclonal method was indicated in this study

. The level of protective immunity in rainbow trout, Salmo gairdneri Richardson, following vaccination by intraperitoneal (i.p.) injection or by direct immersion with Vibrio anguillarum was studied over a period of 46 weeks. Antibody titres to V. anguillarum O‐antigen were determined with ELISA at the time of each experimental infection to study the relation between specific antibody production and protective immunity. Both vaccination by i.p. injection and vaccination by direct immersion induced a high degree of protective immunity against vibriosis which lasted for at least 46 weeks. At each experimental infection, the proportions of seropositive fish were lower than the proportions of fish with protective immunity. However, seropositive individuals were found in both experimental groups throughout the study.

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