Aquaculture is promoted globally to address dwindling capture fisheries, but challenges including bacterial diseases exist and impact on productivity. Existing fish health management strategies, including prophylactic and therapeutic antibiotic use, have shortcomings. Irrational drug use contributes to antibiotic resistance and residues in fish. Thus, alternative disease control approaches, such as use of bacteriophages, are urgently needed. Bacteriophages are viruses that infect specific bacteria. An on-going African Union funded project, Safefish, is implemented in Ghana and Uganda with aims to develop bacteriophage cocktails as fish disease biocontrol agents for integrated fish disease management and minimized antibiotic use, for improved aquaculture productivity among tilapia farmers, in Ghana and Uganda.
Methods: Fish, pond water and sediment; as well as fish feed samples were collected from selected tilapia farms in a survey that covered the different regions of Uganda. Prevalent bacteria were identified and tested for susceptibility to selected antibiotics. Bacteriophages against three most encountered fish pathogens were isolated evaluated their lytic activity by host range and stability at selected physicochemical conditions.
Results: Various Gram-negative pathogens were detected in pond sediments, pond water, fish feed and fish obtained during a survey. The most common encountered were Aeromonas ssp (up to 36%), Edwardsiella spp (up to 24%) and Klebsiella spp (up to 23%). High occurrence of MDR and antibiotic resistance was encountered (Fig.1). Aeromonas- specific bacteriophages analysed indicated up to 65% host range; stability at 20 – 50°C and 60% and 70% survival at -20°C and 4°C, respectively.
Conclusion: High occurrence of AMR augments the need for alternatives to antibiotic use in fish disease management. Bacteriophage analyses on-going to select candidate for formulation of cocktails for use on tilapia farms.
Acknowledgement: Funding agency - European Union and African Union; Conference organisers, WAA