Application of anti-stress products in aquaculture: influence of Propiscin on the effectiveness of an anti-Yersinia ruckeri vaccine in rainbow trout Oncorhynchus mykiss (Wal.)

Abstract

Inducing protection against bacterial diseases in fish culture through the application of specific vaccines is one of the most important prevention methods. However, some immunization techniques actually used under hatchery conditions are not as effective as they should be. Therefore, current research is focusing on how to improve the potency and efficacy of the antigens and how to optimally activate the immune response. In our preliminary study, we determined the influence of the anaesthetic Propiscin (IFI, Poland) on the effectiveness of a vaccine applied by intraperitoneal injection or immersion to rainbow trout (Oncorhynchus mykiss). The fish were vaccinated via injection or immersion with an anti-Yersinia ruckeri vaccine (Sanofi, France) under Propiscin-induced anaesthesia or without it. On day 21 after vaccination, all the fish groups were challenged with live Y. ruckeri bacteria (0.2 ml of bacteria at 1 ´ 106 ml-1). Control groups (only anaesthetized and injected PBS or immersed) were infected but not immunized by vaccine. The blood and pronephros were separated before vaccination (10 fish), 21 days after vaccination (10 fish) and 21 days after the challenge (10 fish). ELISPOT assays for the quantification of total immunoglobulin secreting cell (ISC) and specific antibody secreting cell levels (ASC) were used. The total Ig levels in the serum were also measured by spectrophotometric assay and the titers of anti-Y. ruckeri antibody were measured by the micro-agglutination method. 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 nonspecific and specific immune response and protective effectiveness of vaccine after the challenge with pathogenic bacteria. The highest level of total ISC and specific ASC in fish vaccinated by immersion and injections under anaesthesia were observed. The highest total Ig levels and titers of specific antibody in fish vaccinated under anaesthesia were also observed. Cumulative mortality rates were lowest in the fish vaccinated by injection (5%) and immersion (10%) under anaesthesia as compared with fish vaccinated by injection (20%) and immersion (35%) without anaesthesia. Cumulative mortality in the control, non-vaccinated group of fish was 80%.

CORRESPONDING AUTHOR:

Andrzej K. Siwicki, Instytut Rybactwa Śródlądowego, Zakład Patologii i Immunologii Ryb Żabieniec, ul. Główna 48, 05-500 Piaseczno; Tel./Fax: +48 22 7562490; e-mail:aksiw@infish.com.pl