Efficacy testing of novel immersion and oral vaccines for Aeromonas hydrophila in Tilapia and Vietnamese catfish
In 2014 the contribution of aquaculture to supply food for human consumption overtook that of 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 tilapia and Pangasius (Vietnamese catfish also known as Tra catfish). These fish species are farmed in low and middle-income countries (LMICs) and provide an important source of revenue for many low income families supplying both the domestic and export market. Tilapia production is rapidly increasing with Egypt the third largest global producer. Tilapia and Vietnamese catfish are both produced in Vietnam. Although Vietnamese catfish production increased dramatically between 2004 and 2008, the export market has since levelled off due to public concern over disease and over use of antibiotics. Currently, disease outbreaks caused by Aeromonas hydrophila are having a major economic impact on aquaculture in both countries. No vaccine is currently available in Egypt and despite a vaccine being available for use in Vietnamese catfish, antibiotics remain the treatment of choice due to doubts over vaccine effectiveness (A. hydrophila strains are highly diverse) and the high cost of the vaccine (administered by injecting individual sedated fish). The widespread use of antibiotics within farms can encourage antimicrobial resistance, reducing the treatment options for both fish and human infection. Through a collaboration of scientists from Vietnam, Egypt and the UK we plan to test the efficacy of novel vaccines that can be easily administered (i.e. immersion and oral vaccines), without the need for highly trained personnel and specialist equipment. Such vaccines are urgently needed to help prevent A. hydrophila disease outbreaks and reduce antibiotic use in both tilapia and Vietnamese catfish aquaculture.