The application of finfish vaccines in aquaculture has reduced the use of antibiotics and led to greater disease prevention in farmed fish. Traditional vaccination methods, like injection and immersion (bath) vaccines, have drawbacks that make their use less than ideal in large-scale aquaculture operations. Injectable vaccines, while highly effective, require fish to be individually handled, which is time-consuming and stressful for the animals. Furthermore, these vaccines are most effective when administered to larger fish (typically over 20 grams), limiting their utility in younger or smaller fish. Immersion vaccines, on the other hand, are less labor-intensive but have lower efficacy due to the challenges of ensuring adequate vaccine uptake. In contrast, oral vaccines have the potential to overcome several of these limitations. Oral vaccination methods allow for the administration of vaccines through feed, eliminating the need for injection or fish handling altogether. However, the development of effective oral vaccines has been slow due to challenges with 1) vaccine encapsulation, 2) ensuring fish ingest the vaccines, and 3) achieving sufficient protection of orally vaccinated fish. This project aimed to address these challenges by developing a novel oral vaccine platform that could be used in both freshwater and marine finfish aquaculture systems. Specifically, whole-cell Aeromonas salmonicida vaccines were encapsulated within liposome-based complex particles. The efficacy of this oral vaccine was tested through immune response and pathogen challenge trials with sablefish and trout.
Results from these trials showed that the oral vaccine was as effective as bath vaccines in providing protection against A. salmonicida. Furthermore, the oral vaccines also proved to be effective boosters when combined with other vaccination strategies, offering additional flexibility in managing disease prevention protocols. Despite these promising results, further research is needed to 1) evaluate this platform for use with additional pathogens and 2) optimize the oral vaccination methodologies and formulations for improved economy. However, once these challenges are overcome, this oral vaccine platform presents a potential tool for finfish aquaculture by offering a versatile and non-invasive vaccination strategy. It could significantly reduce labor costs, improve animal welfare, and further reduce reliance on antibiotics, which are key goals in sustainable aquaculture practices. In conclusion, the oral vaccination platform developed in this project holds promise for improving disease management in aquaculture, offering an alternative to immersion-based methods, and possibly transforming the way vaccines are administered in commercial fish farming.