Promoting the use of vaccines in tilapia aquaculture
An International Veterinary Vaccinology Network (IVVN) funded workshop on ‘Prompting the use of vaccines in tilapia Aquaculture’ held at Hue University of Agriculture and Forestry, Vietnam, 29th-31st October 2018.
Dr Nguyễn Ngọc Phước, Hue University of Agriculture and Forestry, Vietnam and Dr Kim Thompson, Moredun Research Institute (MRI), UK, hosted a workshop at Hue University of Agriculture and Forestry on 29th-31st October 2018 entitled 'Promoting the use of vaccines in tilapia Aquaculture'. This three-day workshop was held as part of their IVVN pump-priming project 'Development of immunological tools for monitoring the immune response of Nile tilapia', led by Dr Thompson. Other project partners who attended included Dr Fred Fellouse from the University of Toronto, Canada, and Dr Nguyen Duc Hoang from Vietnam National University, Ho Chi Minh City, Vietnam.
Tilapia is an attractive species for aquaculture, reaching harvest size in 6-7 months, and it is now the second most predominant aquaculture species globally after carp. They are farmed in many low and middle-income countries (LMICs) and provide an important source of revenue for many low income families. Disease in tilapia culture is associated with intensification of the farming system, and both bacterial and viral diseases are severely impacting on the expansion of tilapia farming. There is increasing concern about the use of antibiotics to control disease outbreaks and attention is focusing on the use of vaccination for disease control. Vaccination exposes fish to a non-infectious dose of the pathogen, so when they come into contact with the pathogen at a later date, their immune system's memory cells stimulate a response to combat the disease. We need a better understanding of how immune cells respond to infection and vaccination to be able to develop and formulate effective vaccine products for tilapia. We have few reagents available for investigating the immune response of tilapia, however. Through the collaboration of scientists from Vietnam, Canada and the UK, we are developing a range of synthetic antibodies in our IVVN pump-priming project for studying the immune response of this important aquaculture species. Synthetic antibodies are made in the laboratory, unlike conventional antibodies, which are produce in animals, thus eliminating the need to use animals to make these reagents. The targets for antibody production include CD3ε, CD4, CD8 (T-cells); CD172 (SIRPα – dendritic cells); CD45 (leukocytes) and CD163 (macrophages).
A total of 42 scientists attended the workshop, which was open to fish health scientists and fish immunologists in the region through additional funding awarded to Dr Nguyễn Ngọc Phước from the IVVN’s workshop fund and through the Belgian funding programme VLIR-IUC. As well as project partners, 35 scientists were invited from Vietnam, and 7 scientists from around the region, including Bangladesh, Malaysia, Indonesia and Thailand (Figure 1). The purpose of the workshop was to promote the use of vaccines in tilapia aquaculture, to inform delegates of the results of this IVVN project, and for scientists within the region to present updates on the disease status of tilapia aquaculture in their country. There was also discussion on how scientists could help validate the antibodies in their vaccination trials and if the consortium could find follow-on funding for this activity.
- Dr Nguyễn Ngọc Phước's research interests focus on improving aquatic animal health, especially on bacterial diseases of economically important farmed aquatic species in Vietnam. He is currently working on fish disease research, including experimental challenges, epidemiological and pathological studies of novel bacterial diseases in aquatic animal production in Vietnam. He gave an overview on 'Aquaculture in Vietnam' and presented 'A case study on developing and improving sustainable aquaculture with emphasis on bottom-up solutions for environmental pollution in Thua Thien Hue province'.
- Dr Kim Thompson is a Principal Investigator within the Aquaculture Research Group at MRI. She has published more than 140 publications relating to fish immunity, focusing on vaccine development, effects of immunostimulants and feed additives on the immune system and disease resistance of fish. She chaired the workshop and presented talks on 'The immune response of tilapia' and 'An overview on the application of vaccines in aquaculture'.
- Dr Frederic Fellouse generates antibodies using synthetic antibody technology and has generated of thousands of antibodies with high specificity and affinity against hundreds of targets, mostly related to human health. In the past three years, Dr Frederic Fellouse has applied this technology for veterinarian and infectious disease applications: serotype specific dengue fever diagnostic, epitope focused immunogen for dengue and east coast fever, recombinant antibody of bovine antibodies. He presented 'An overview on the production of synthetic antibodies'.
- Prof Md Sabri Bin Mohd Yusoff is a veterinarian working at Department of Veterinary Pathology & Microbiology, Universiti Putra Malaysia (UPM). One of his research interests focuses on streptococcosis infections in tilapia and in his talk, entitled 'Streptococcus vaccine in Malaysia', he discussed an oral vaccine he had developed with colleagues at UPM.
- Dr Channarong Rodkhum is a professor in the Department of Veterinary Microbiology at Chulalongkorn University, Thailand. His research focuses on infectious diseases of aquatic animals, pathogenesis and molecular biology of aquatic pathogens, current diagnostic methods, prevention and treatment of bacterial diseases of aquatic animals, and antimicrobial resistance. His talks included 'Integration of knowledge in molecular genetics and virulence of Flavobacterium columnare for development of vaccine against columnaris diseases in tilapia', 'Development of immersion formalin killed nano vaccine against Flavobacterium columnare in tilapia' and 'Nanomedicine-based drug and vaccine delivery system for aquatic animals'.
- Dr Pattanapon Kayansamruaj is a professor in Veterinary Science, at Chulalongkorn University. His major research interest involves veterinary microbiology. He made his mark in the scientific community with a wide range of contributions for which he has gained wide recognition. Dr Pattanapon has received several awards for his contribution to the scientific community. He presented 'Current epidemiological situation of infectious diseases threatening fresh-water farmed Asian sea bass (Lates calcarifer) in Thailand'.
- Prof Md. Ali Reza Faruk is a professor in the Department of Aquaculture at Bangladesh Agricultural University. His research interests include aquatic animal health management, molecular mycology, development of immuno-diagnosis, and characterisation of aquatic pathogens. He presented 'An overview of aquaculture and fish disease in Bangladesh'.
- Dr Duy Le is a lecturer in fish diseases at the Faculty of Fisheries, Hue University of Agriculture and Forestry, Vietnam. His main areas of research are fish diseases diagnosis, microbiology and gut microbiome of fish. He presented 'Live food and the use of probiotics in rabbit fish larviculture'.
- Prof Nguyen Duc Hoang is an expert in bacterial genetics, protein expression and purification. His group works on the development of expression systems, engineering, production, and characterization of proteins. These include the development of bacterial expression vectors, generation of recombinant bacteria for production of recombinant proteins in Bacillus subtilis. Some of the potential recombinant proteins are produced from infectious diseases for vaccine development. His talk was entitled 'Novel technologies for vaccine development'.
Discussions at the workshop
Some important points were discussed at the workshop with respect to administering vaccines to tilapia:
- A lot of farmers will not vaccinate by injection once the fish are in the farm, firstly because the culture period is so short for tilapia and secondly because it is logistically difficult to vaccine fish once they are in their grow-out site.
- The ideal solution is to vaccinate fish in the hatchery before they are moved for grow-out, around one-month post-hatch. Injection is difficult in small fish. Vaccinating the brood stock may potentially be an option.
- Alternative vaccine delivery methods are needed for tilapia, such as nanoparticle delivery which can be applied orally or by immersion.
- Vaccines for tilapia need to be cheap because it is such a low value species, otherwise the farmer will not be willing to pay for the vaccine.
- Concurrent infections are now the norm in tilapia culture. These complicate vaccine design, making vaccines more expensive and the co-infections can affect the fish’s ability to response to the vaccine. Only healthy fish should be vaccinated for an optimal immune response to be induced by the vaccine.
- The major pathogens currently causing big problems in tilapia culture in Southeast Asia include Streptococcus agalactiae (especially serotypes Ia and III) Steptococcus iniae, Aeromonas (especially Aeromonas veronii), Edwardsiella spp, (E. tarda and E. ictaluri), Mycobacterium marinum, iridovirus and Francisella noatunesis subsp. orientalis (Fno). Farmers are seeing a big increase in Flavobacterium columnareoutbreaks often in concurrent infections with Fno.
On the third day of the workshop, the delegates had the opportunity to visit aquaculture sites near Hue to observe the disease problems in tilapia farms first hand, including two tilapia farms (Figure 2).
If you would like to know more about the IVVN project or are interested helping to evaluate the MAbs please contact Kim Thompson (kim [dot] thompson [at] moredun [dot] ac [dot] uk).