Immunopotential Induced in Culturable Carps Fed on Edible Bivalent Vaccine Against Aeromonas veronii and Aeromonas hydrophila

The bacterial pathogens Aeromonas species, notably Aeromonas veronii and Aeromonas hydrophila, are major causative agents of severe infections and significant mortalities in freshwater aquaculture systems. Vaccination offers an effective prophylactic approach to enhance fish immune defenses and reduce reliance on antibiotics. This study aimed to evaluate the immunoprotective efficacy of a bivalent bacterial oral vaccine against these pathogens in carps. The vaccine was formulated by either incorporating or spraying it/onto commercial feed (30% crude protein), with 10% fish oil and mineral oil added as adjuvants. Seven experimental dietary diets were designed, comprising vaccinated feeds administered with or without adjuvants (1 mL of vaccine per gram of feed) and a nonvaccinated control. Healthy fingerlings (20 ± 5 g) were fed their respective diets over a 60-day experimental period, followed by challenge with Aeromonas spp. To evaluate the effectiveness of the vaccination, immune parameters (serum lysozyme activity, agglutination antibody titers, and IgM levels), growth performance (net weight gain [NWG], specific growth rate [SGR], and feed conversion ratio [FCR]) and survival rates were examined. In comparison to the control, the results indicated that all vaccination diets showed considerably improved immune responses and growth. However, vaccinated diet with fish oil (IVFF) showed the highest immunological stimulation and rate of survival, 83% for Ctenopharyngodon idella (C. idella) and 85% for Labeo rohita (L. rohita). These results validate the IVFF oral vaccine formulation has potential as a noninvasive, scalable method of providing protective immunization against Aeromonas infections in freshwater aquaculture.