Efficacy testing of immersion and oral vaccines for Aeromonas hydrophila in Tilapia an Vietnamese catfish

In 2014 the contribution of aquaculture to supply food for human consumption overtook that for wild-caught fish for the first time. Aquaculture currently contributes approximately 73.8 million Tonnes of aquatic animals with a value of US$ 130 billion. This has increased by 10-12% from 59 million tonnes in 2011, representing the fastest growing animal production sector. Over 30 species are currently farmed, including with tilapia and Pangasius (Vietnamese catfish) (FAO, 2016). These fish species are farmed in low and middle-income countries (LMIC) and provide an important source of revenue for many low income families. Globally tilapia production is rapidly increasing with Egypt the third largest producer. In contrast Pangasius production increased dramatically between 2004 and 2008 and then levelled off as export requirements have decreased due to public concern over disease and over use of antibiotics. Currently, disease outbreaks caused by bacterial pathogens, in particular Aeromonas hydrophila, are having a major economic impact on both the tilapia and the Vietnamese catfish industries. Despite a vaccine being available against A. hydrophila for use in Vietnamese catfish, antibiotics remain the treatment of choice due to doubts over vaccine effectiveness (A. hydrophila strains are highly diverse) and high cost of the vaccine (administered by injecting individual sedated fish). The widespread use of antibiotics within farms can encourage anti- microbial resistance, reducing the treatment options for both fish and human infections.
This project aims to test the efficacy of vaccines that can be easily administered (immersion and oral vaccines), without the need for highly trained personnel and specialist equipment; such vaccines are urgently needed to help tackle A. hydrophila infections and reduce antibiotic use in both tilapia and Pangasius aquaculture.