Effect of vaccination against yersiniosis on the relative percent survival, bactericidal and lysozyme response of Atlantic salmon, Salmo salar

• Published in: Aquaculture
• Main Authors: Costa, AA, Leef, MJ, Bridle, AR, Carson, J, Nowak, BF
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Bv 2011
• Subjects: Agricultural and Veterinary Sciences; Fisheries Sciences; Fish Pests and Diseases; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.1016/j.aquaculture.2011.02.031; http://ecite.utas.edu.au/71987

The bacterium Yersinia ruckeri serovar O1b causes yersiniosis in Atlantic salmon, Salmo salar , in the southernhemisphere. Despite vaccination this disease has resulted in significant hatchery losses in the TasmanianAtlantic salmon aquaculture industry. A poor response to vaccination in juveniles, 15 g, has lead to theinvestigation of the suitability of the current formalin killed whole-cell vaccine Yersinivac-B. In this studytrypsin was added to the Yersinivac-B to expose the bacteria's protective O-antigen to make the vaccine moreimmunogenic. At six weeks post vaccination, the effect of Yersinivac-B and the novel trypsinated Yersinivac-Bvaccine on body mucus lysozyme and mucus and serum bactericidal activity of fish was determined over a48 h period following challenge with Y. ruckeri . Body and gill mucus lysozyme and mucus and serumbactericidal activity was also determined in surviving fish at 10 weeks post Y. ruckeri challenge. Following thechallenge period of 14 days the trypsinated Yersinivac-B fish demonstrated a significantly higher percentsurvival compared to the Yersinivac-B and control unvaccinated fish. Body mucus lysozyme concentrationwas also significantly elevated at 8 h post challenge in the trypsinated Yersinivac-B fish compared to controls.This variable however appears unlikely to play a significant role in protection as positive bactericidal activitywas not found in the mucus of any fish following challenge. Bactericidal activity was not observed in theserum or mucus of any challenge survivors. At 8 h post challenge the trypsinated Yersinivac-B fishdemonstrated the highest serum bactericidal activity. However, the unvaccinated control fish also displayedpositive serum bactericidal activity despite being unlikely to have been previously exposed to Y. ruckeri . Asignificantly higher gill mucus lysozyme concentration in control survivors compared to vaccinated fishsuggests that this response may be important in the protection of unvaccinated fish against yersiniosis. Thisresearch has highlighted the potential use of trypsin to increase the efficacy of Yersinivac-B. It has alsocontributed to better understanding of the role of humoral immune responses during a Y. ruckeri challenge.