How to help the anti-infective immunity of European carp

Mara Thomas, Justyna Andrysiak, Proteon Pharma

The excessive use of antibiotics has triggered the development of resistance in bacteria rendering most antibiotics partially or completely ineffective. The aquaculture industry is greatly responsible especially due to the overuse of antibiotics. In 2016, Chile used 382.5 tons of antibiotics for the salmon industry alone (Miranda et al. 2018). Antimicrobial resistance (AMR) also has a substantial economic impact. In Chile, the AMR crisis of 2009, dropped the value of their production by $2 billion until 2011 (Asche et al. 2009). This has revealed a necessity for innovative alternatives to help tackle the AMR threat. Bacteriophages, simply called phages, are viruses that attack only bacteria. They help eliminate excessively multiplying bacteria that could lead to pathological conditions without disturbing the microbiome, as antibiotics do. As they are naturally occurring in the environment, they pose little to no threat of developing resistance. BAFADOR® is a bacteriophage cocktail that targets Aeromonas and Pseudomonas bacteria and helps strengthen the fish’s immune system. This study aims to assess its efficacy as a feed additive used prophylactically in European carp.

Methodology

This study used 180 healthy carp (Cyprinus carpio). Upon their arrival, they were randomly split into three groups, each with 3 repetitions and they all underwent an acclimatization period of 12 days. They were kept in 180L tanks at a temperature of 18,6°C and were fed Ofeedo Extracarp 25 commercial diet manually.

Figure 1. Mortality after infection with mix of A. hydrophila and P. fluorescens.

The average weight of fish was 80,15 g.

The negative control groups were neither infected nor treated. The positive control groups were infected by intraperitoneal injection with an Aeromonas hydrophila and Pseudomonas fluorescens mix but were not given the prophylactic feed additive. The experimental groups were also infected with the same mix but were additionally given BAFADOR® mixed with the feed, in the amount of 0.02ml/fish. BAFADOR® was given 5 days before the experimental infection and daily after, at the same dose, for the remaining time of the experiment. The mortality in each group was recorded for 21 days in order to determine if BAFADOR® was effective in helping the immune system of carps and preventing bacterial infection. The study lasted a total of 40 days.

Results

As can be seen in Figure 1, the experimental groups (3a, 3b and 3c) which were given BAFADOR® did not record any mortality during the experiment. In comparison, the positive control groups (2a, 2b and 2c) which were infected but did not receive the bacteriophage cocktail had an average mortality of 15%. BAFADOR® helped prepare the carp’s immune system and was effective in preventing infection by A. hydrophila and P. fluorescens. In addition, the water analysis showed that BAFADOR® was successfully absorbed by the feed, confirming this application method was the most suitable.

Conclusion

The results of the experiment show that BAFADOR® is an effective solution for the prevention of A. hydrophila and P. fluorescens infections. The low mortality rates in the groups where BAFADOR® were administered compared to the infected control show the positive contribution of BAFADOR® to the fish’s immune system and general wellbeing. Improving the general health status of fish as well as lowering mortality rates among farmed fish can contribute to a better quality of production and financial savings to the farmer.

References

Asche, F., Hansen, H., Tveteras, R. and Tveterås, S., 2009. The salmon disease crisis in Chile. Marine Resource Economics, 24(4), pp.405-411. Miranda, C.D., Godoy, F.A. and Lee, M.R., 2018. Current status of the use of antibiotics and the antimicrobial resistance in the Chilean salmon farms. Frontiers in microbiology, 9, p.1284.

More information: Justyna Andrysiak

Chief Product Developments Officer Proteon Pharma, Poland E: proteon@proteonpharma.com