{"id":2754,"date":"2025-09-17T17:06:33","date_gmt":"2025-09-17T10:06:33","guid":{"rendered":"https:\/\/green.msu.ac.th\/?p=2754"},"modified":"2025-09-17T17:06:35","modified_gmt":"2025-09-17T10:06:35","slug":"vaccine-development-for-the-prevention-of-streptococcosis-in-nile-tilapia","status":"publish","type":"post","link":"https:\/\/green.msu.ac.th\/?p=2754","title":{"rendered":"Vaccine Development for the Prevention of Streptococcosis in Nile Tilapia"},"content":{"rendered":"\n

At present, Streptococcosis disease is considered one of the most serious challenges affecting Nile tilapia farming in Thailand, especially in the northeastern region, where tilapia is a major economic species that continually provides income for farmers. The disease is caused by the bacterium Streptococcus agalactiae, which leads to high mortality rates on farms, reducing yields and threatening the nation\u2019s food security. Developing an effective vaccine to prevent this disease has therefore become an essential approach to strengthening the quality and sustainability of aquaculture.<\/p>\n\n\n\n

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Assoc. Prof. Dr. Ekaphon Wangkahart, a faculty member in the Department of Agricultural Technology, Fisheries Program, Faculty of Technology, Mahasarakham University, has conducted research and development of a vaccine to prevent streptococcosis in Nile tilapia. His work focuses on building effective immunity in fish that is safe and environmentally friendly. Beyond reducing the use of antibiotics in aquaculture, this research also has the potential to be expanded into large-scale vaccine production. It represents a significant achievement in applied research that truly benefits both local communities and the nation.<\/p>\n\n\n\n

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Motivation and Key Issues Behind the Development of a Vaccine Against Streptococcosis in Nile Tilapia<\/strong><\/p>\n\n\n\n

The motivation for developing a vaccine against streptococcosis in Nile tilapia stems from the severe outbreaks that have struck fish farms in Thailand. These outbreaks cause mass fish mortality and result in enormous economic losses. To cope, many farmers have become overly dependent on antibiotics, leading to problems of drug resistance and chemical residues. Developing a vaccine offers a sustainable solution\u2014helping to prevent disease, reduce antibiotic use, and strengthen fish immunity. This initiative has also gained support from the government, encouraging researchers to work toward effective vaccine development for disease prevention.<\/p>\n\n\n\n

Impact of Streptococcosis on the Tilapia Farming Industry in Thailand<\/strong><\/p>\n\n\n\n

Streptococcosis has a severe impact on Thailand\u2019s tilapia farming industry, causing mortality rates as high as 50\u2013100%, particularly in high-density farming systems. This results in heavy financial losses for farmers and directly affects Thailand\u2019s tilapia exports. Outbreaks of the disease also undermine confidence in international markets, making it a critical issue that must be effectively controlled to ensure the long-term sustainability of the industry.<\/p>\n\n\n\n

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Previous Methods of Prevention and Treatment, and Their Limitations<\/strong><\/p>\n\n\n\n

In the past, the main methods for preventing and treating streptococcosis in Nile tilapia were the use of antibiotics to control infection and good farm management practices, such as reducing stocking density and monitoring water quality. However, these approaches have several key limitations:<\/p>\n\n\n\n

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  1. Development of antibiotic resistance due to repeated use.<\/li>\n\n\n\n
  2. Residues in fish meat, which affect consumer safety and export standards.<\/li>\n\n\n\n
  3. High costs, with no permanent control of the disease.<\/li>\n\n\n\n
  4. No stimulation of fish immunity, leaving farms vulnerable to recurring outbreaks.<\/li>\n<\/ol>\n\n\n\n

    For these reasons, more attention has recently been given to vaccine development as a sustainable approach to disease prevention.<\/p>\n\n\n\n

    Scientific Techniques Used in Vaccine Development<\/strong><\/p>\n\n\n\n

    The vaccine against streptococcosis in Nile tilapia was developed as an inactivated vaccine<\/em>, using Streptococcus agalactiae<\/em> isolated from naturally infected fish on farms. The bacteria were inactivated with chemicals, preserving their antigen structure, then combined with an immune-stimulating adjuvant and tested in tilapia.<\/p>\n\n\n\n

    In this research, three methods of vaccine delivery were developed: injection, immersion, and incorporation into feed. The results showed that the vaccine is safe, easy to use, significantly reduces fish mortality, and clearly decreases the need for antibiotics in farming. These features make it well-suited for real-world commercial application.<\/p>\n\n\n\n

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    Selection of Streptococcus Strains for the Research<\/strong><\/p>\n\n\n\n

    In this study, the selection of Streptococcus<\/em> strains focused on those that cause severe disease in Nile tilapia from actual outbreak farms. This ensures that the developed vaccine matches the strains commonly found in natural conditions. The selected strains were further examined for their genetic characteristics and pathogenicity to identify the most suitable candidates for vaccine development.<\/p>\n\n\n\n

    Type of Vaccine Developed<\/strong><\/p>\n\n\n\n

    In aquaculture, several types of vaccines are used. These include inactivated vaccines, which use killed pathogens and are safe and easy to apply; live attenuated vaccines, which use weakened pathogens that trigger stronger immunity but carry higher risks; protein or purified antigen vaccines, which use only specific parts of the pathogen for greater safety; and DNA vaccines, which employ fragments of the pathogen\u2019s DNA and are still largely in the research stage. In addition, multivalent vaccines combine antigens from several pathogens into a single formulation to protect against multiple diseases at once.<\/p>\n\n\n\n

    The vaccine developed in this research is an inactivated vaccine<\/strong>, made from Streptococcus<\/em> bacteria that have been killed but still retain their antigenic properties to stimulate immunity in Nile tilapia. It offers high safety and is one of the most widely used approaches for preventing this disease.<\/p>\n\n\n\n

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    Timeline from Project Start to Vaccine Trials in Fish<\/strong><\/p>\n\n\n\n

    The period from the beginning of the research project to vaccine trials in Nile tilapia took about two to three years. In fact, the work began in 2020 and included several steps: strain selection, vaccine development, safety testing, and evaluation of vaccine effectiveness in experimental fish.<\/p>\n\n\n\n

    Vaccine Efficacy Testing: Laboratory and Field Levels<\/strong><\/p>\n\n\n\n

    The research tested the efficacy of the developed vaccine in two stages:<\/p>\n\n\n\n

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    1. Laboratory Testing<\/strong>: Initial tests were carried out in the laboratory to evaluate basic safety and preliminary effectiveness. This included examining the immune response in Nile tilapia and assessing how the vaccine reacted against\u00a0Streptococcus agalactiae<\/em>.<\/li>\n\n\n\n
    2. Field Trials<\/strong>: After laboratory testing, the vaccine was tested in real farm conditions at Ubolratana Dam in Khon Kaen Province. These trials assessed the vaccine\u2019s effectiveness in preventing streptococcosis under actual farming environments, such as survival rates and reduced infection rates. Economic evaluations of cost-effectiveness were also conducted.<\/li>\n<\/ol>\n\n\n\n

      Testing at both levels provided a comprehensive assessment of the vaccine\u2019s safety and effectiveness before moving toward commercial use and large-scale production.<\/p>\n\n\n\n

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      Field Trial Results on Mortality Reduction<\/strong><\/p>\n\n\n\n

      Field trial results showed that the vaccine reduced mortality in Nile tilapia by about 50\u201360% compared to the unvaccinated control group. This demonstrates that the vaccine significantly improves fish survival rates under real farming conditions.<\/strong><\/p>\n\n\n\n

      Long-Term Safety and Side Effects<\/strong><\/p>\n\n\n\n

      Research findings indicate that this inactivated vaccine is highly safe, with no significant side effects or long-term impacts on Nile tilapia. After vaccination, the fish continued to grow normally and showed no abnormalities related to the vaccine. Therefore, it is considered both safe and suitable for use in tilapia farming.<\/p>\n\n\n\n

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      Reduction of Antibiotic Use and Farm Costs<\/strong><\/p>\n\n\n\n

      The vaccine significantly decreases the need for antibiotics in Nile tilapia farms. Since vaccinated fish show lower infection and mortality rates, farmers can reduce both medication use and treatment costs. It is estimated that the vaccine can cut antibiotic use by 40\u201350% in farms where it is applied consistently.<\/p>\n\n\n\n

      Plans for Technology Transfer and Commercial Production<\/strong><\/p>\n\n\n\n

      This vaccine shows strong potential for commercial use because of its advantages. One is the option of oral administration by mixing it into feed, which eliminates the need for injections and reduces labor and management costs. Another is the use of adjuvants that enhance immune response, making the vaccine more effective and extending disease resistance.<\/p>\n\n\n\n

      Commercial development, however, requires several steps: large-scale production, safety and efficacy testing under real farming conditions, and regulatory approval from relevant authorities. With government support and collaboration from the private sector, this vaccine has a promising future for commercial application in Nile tilapia farms. Technology transfer and commercial-scale production are expected to follow, making the vaccine available for practical use in aquaculture.<\/p>\n\n\n\n

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      Improving Farmers\u2019 Quality of Life<\/strong><\/p>\n\n\n\n

      This research helps improve the quality of life for tilapia farmers by providing an effective vaccine against streptococcosis. Healthier fish with lower mortality rates lead to higher yields. Farmers benefit from reduced antibiotic use, lower production costs, and increased income from fish sales. In addition, the vaccine builds greater confidence in both domestic and international markets.<\/strong><\/p>\n\n\n\n

      Collaboration with Local Farmers in Field Trials<\/strong><\/p>\n\n\n\n

      Field trials were carried out in real tilapia farms at Ubolratana Dam in Khon Kaen Province, where the fish were raised in cages. The trials were conducted in close collaboration with farmers and farm owners, who kindly supported the project throughout the five-month testing period. This partnership made it possible to evaluate the vaccine\u2019s effectiveness under real farming conditions.<\/p>\n\n\n\n

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      Training and Knowledge Transfer for Farmers<\/strong><\/p>\n\n\n\n

      In the process of applying the vaccine in real farms, training and knowledge transfer for farmers are essential steps. These activities usually go hand in hand with the commercial development of vaccines to ensure correct use and maximum effectiveness. If this vaccine enters production and distribution in the future, it is expected that relevant agencies, both public and private, will organize training programs for farmers.<\/p>\n\n\n\n

      Farmers\u2019 Feedback and Suggestions<\/strong><\/p>\n\n\n\n

      If the vaccine is applied in real farms, it is expected that farmers\u2019 feedback will be collected on issues such as:<\/p>\n\n\n\n