Abstract
The aquaculture industry is responsible for producing over 50% of all seafood for human consumption, worth over $1.5 B in 2020 in the US alone. Fish farming practices of this caliber can raise hundreds of thousands of fish at a time, but living in such close quarters can lead to a devastating consequence: disease transmission and catastrophic losses. To minimize losses in aquaculture due to disease, vaccines are widely used. The number of vaccines developed for aquaculture is increasing, and there is a move to incorporate many different vaccines into a single dose to improve cost-effectiveness and minimize stress from handling. However, while multivalent vaccines may have their delivery efficiencies, we must understand whether they are as effective as single-target (monovalent) vaccines. For my master’s project, we chose three pathogens, Aeromonas salmonicida, Vibrio anguillarum, and Yersinia ruckeri, which cause significant losses in rainbow trout aquaculture, and developed three monovalent vaccines and one trivalent vaccine consisting of a cocktail of the three bacteria, and examined the antibody responses to these vaccines over time. We found that when a vaccine was delivered as part of a multivalent cocktail, rainbow trout could not respond as effectively to the individual components of the vaccine compared to animals vaccinated with a single target. Reductions in antibody concentrations were significant, with a greater than 20-fold decrease in circulating antibodies in response to one of the vaccines. A different target, Vibrio anguillarum, dominated the antibody response over the other two antigens in the multivalent vaccine. The significance of these results will be discussed in the context of current literature on antigen dominance, original antigenic seniority, and the direction the aquaculture industry should take in developing new vaccines.