Reducing antibiotic use in tilapia aquaculture through scalable vaccination strategies
Nguyen Tien Vinh1, Nguyen Giang Thu Lan1*, Janchai Wongkaew1, Suryasnata Das1, Vaishnavi Manoj Kolvankar1, Satid Chatchaiphan2, Jessica Kaye Turner3, Saengchan Senapin4,5, Sophie St-Hilaire6, Krishna R. Salin1, Channarong Rodkhum7,8, Warren Andrew Turner3, Ha Thanh Dong1Rym Essid1, Ameni Ayed1, Ghofran Atrous1, Nadia Feris1, Olfa Tabbene1
1Aquaculture and Aquatic Resources Management, Faculty of Food, Agriculture and Natural Resources, Asian Institute of Technology, Pathum Thani, Thailand
2Department of Aquaculture, Faculty of Fisheries, Kasetsart University, Bangkok, Thailand
3Nam Sai Farms Co., Ltd. Prachinburi, Thailand
4National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani, Thailand
5Fish Health Platform, Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Faculty of Science, Mahidol University, Bangkok, Thailand
6 Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon Tong, Hong Kong SAR PR China
7The International Graduate Program of Veterinary Science and Technology (VST), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand
8Center of Excellence in Fish Infectious Diseases (CE FID), Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand
Streptococcosis caused by Streptococcus agalactiae remains a major constraint in tilapia aquaculture, particularly in Southeast Asia where serotype variation and limited vaccine accessibility hinder effective disease control. Although advanced vaccine technologies are available, their adoption in tilapia farming is often limited by cost and practicality, highlighting the need for simple, scalable, and cost-effective solutions. In this study, we developed and evaluated a locally adaptable bivalent heat-killed vaccine (serotypes Ia and III) under laboratory and field conditions using different delivery strategies. Through tradition injection vaccination comprising a priming and a boosting dose, the vaccine elicited robust IgM antibody in tilapia (Oreochromis niloticus) under laboratory conditions up to day 84; and conferred a relative percent survival (RPS) of 86.8-100%. During farm trials across two red tilapia cage systems, the injection-based approach sustained long-term antibody levels and conferred high protection, achieving a relative percent survival (RPS) of 83.4-85.7%. Additionally, this method increased production by 25-45% and doubled profit margins. To promote scalability and reduce handling stress, we further explored a non-invasive delivery approach using a novel nanobubble-assisted immersion priming followed by oral boosting. In the lab, nanobubble-assisted-vaccine groups, including oxygen nanobubble combined with chitosan and vaccine (O2NB-CS-Vac) and ozone nanobubble pre-treatment followed by oxygen nanobubble combined with chitosan and vaccine, O3NB-(O2NB-CS-Vac), showed enhanced innate immune responses and moderate protection (RPS 55.56-63.16%) compared to the non-nanobubble immersion group (RPS 16.67-36.84%). Under field conditions, the nanobubble-assisted vaccination produced variable and generally low antibody responses, resulting in limited protection relative to controls. Nevertheless, short-term immune elicitation and vaccine protection were observed across most farms for up to 60 days, evidenced by increased lysozyme activity, the upregulation of immune-related genes (IL1β, CD4, CD8, and IgT), and RPS of 42.86-70% during laboratory challenges on a subset of farmed fish. Overall, the locally produced bivalent heat-killed vaccine provides a highly effective, and feasible solution for controlling streptococcosis in tilapia through injection approach. While nanobubble-assisted mucosal vaccination represents a promising non-invasive alternative, further optimization, particularly of booster strategies to prolong the fish immunity, is required to achieve reliable field-level protection.
