Oral vaccination against yersinia ruckeri: oxidative stress biomarkers in the gills of rainbow trout (oncorhynchus mykiss walbaum)

The aim of this study was to assess the effect of oral vaccination against Yersinia ruckeri based on oxidative stress biomarkers in the gills of rainbow trout (Oncorhynchus mykiss Walbaum). The vaccine consisted of three Y. ruckeri strains (O1 serotype) that originated from rainbow trout cultured on different farms, where fish exhibited clinical signs of enteric redmouth disease. The concentrated vaccine was incorporated into the fish food; treatment was delivered three times at one-day intervals. Two months after immunization, gills were sampled. The vaccination against Y. ruckeri resulted in non-significant changes in TBARS level as lipid peroxidation marker, aldehydic and ketonic derivatives of oxidatively modified proteins level in the gills of trout at the second month after immunization against Y. ruckeri. A significant decrease in superoxide dismutase activity (by 36%, p = 0.002) compared to untreated controls occurred. The alterations in markers of oxidative stress suggest that antioxidant defenses may contribute to the balance between oxidative modification of proteins and antioxidant defenses in the gills of trout vaccinated against Y. ruckeri. We did not find any alterations in the gills after 60 days of immunization. This is likely a result of long-term adaptation to immunization. Understanding the role of oxidative stress in the tissues of vaccinated trout has important implications for the understanding of the complex physiological changes that occur in immunization and also for improving aquaculture practices to maximize tissue growth and health of vaccinated trout. The oxidative stress biomarkers in the gills were sensitive to vaccination against Y. ruckeri and may potentially be used as biomarkers in evaluating vaccine toxicity in rainbow trout. From a practical point of view, the results may be useful in relation to studies of infections and the development, administration, and uptake of new vaccines applicable to large amounts of fish.