Assessment of immune response and protection against bacterial coldwater disease induced by a live-attenuated vaccine delivered orally or intraperitoneally to rainbow trout, Oncorhynchus mykiss (Walbaum)

F. psychrophilum is the causative agent of bacterial coldwater disease (BCWD), which is a significant impediment to salmonid aquaculture worldwide. In this study, we evaluate the protection and antibody response against BCWD elicited in rainbow trout by immunisation with a live attenuated strain of F. psychrophilum, delivered by oral or intraperitoneal injection routes. In addition, we assess the effect of alginate microencapsulation on the efficacy of this vaccine candidate. We show that it is possible to elicit both an antibody response and measurable reduction in mortality by oral administration of the vaccine, even under elevated pathogenic challenge pressure.