Inducing protection against bacterial diseases in fish culture by specific vaccines is one of the most important prevention methods. But some immunization techniques actually applied to hatchery conditions are not as effective as they should be. Therefore, research is concentrating on how to improve the potency and efficacy of the antigens and how to optimally activate the immune response. In our study, we continue the study about effect of anaesthetic named Propiscin (IFI, Poland) on the effectiveness of vaccine applied by immersion in rainbow trout (Oncorhynchus mykiss). Fish were vaccinated by immersion with vaccine anti-Aeromonas salmonicida (Furogen Immersion, Aqua Health, Canada) in or without anaesthesia with Propiscin. On day 28 after vaccination, all groups of fishes were challenged with live bacteria Aeromonas salmonicida (0.1 ml of bacteria at 1×106 ml^-1). Control groups (only anaesthetized) were infected but not immunized by vaccine. The blood and pronephros were separated from 10 fish of each group before vaccination and 21, 28, 35 and 60 days after vaccination. The ELISPOT assays for the quantification of total immunoglobulin secreting cells (ISC) and specific antibody secreting cells level (ASC) were used. Also the titres of anti-Aeromonas salmonicida antibody by micro-agglutination method was examined. Mortalities were collected and tabulated and the presence of pathogen was confirmed by isolation from fish kidneys. The results of this study showed that Propiscin applied at vaccination time increased the specific immune response and protective effectiveness of vaccine after challenge with pathogenic bacteria. The higher levels of total ISC, specific ASC and titres of specific antibody in fish vaccinated in anaesthesia were observed. Cumulative mortality rates were lowest in the fish vaccinated in anaesthesia (10%), compared with fish vaccinated without anaesthesia (30%). Cumulative mortality in control non-vaccinated group of fish was 85%.

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