Borneo herbal plant extracts as a natural medication for prophylaxis and treatment of Aeromonas hydrophila and Pseudomonas fluorescens infection in tilapia ( Oreochromis niloticus) [version 1; peer review: 2 approved with reservations]

Background: This study aims to describe the antibacterial and immunostimulant abilities of Boesenbergia pandurata (BP), Solanum ferox (SF) and Zingiber Zerumbet (ZZ) plant extracts to treat and prevent Aeromonas hydrophila and Pseudomonas fluorescens infection on Tilapia ( Oreochromis niloticus). Methods: Tilapia (initial weight 15±2 g) were injected intramuscularly (0.1 ml/fish) with a combination of A. hydrophila and P. fluorescens at a density of 1×10 5 CFU ml -1 of each bacteria. Treatment trials were performed at day 7 post-injection with each combined extract, while the prevention trial was performed by including the combined extract into the diet for six and seven days prior to injection. Various combinations of extract-60 ml SF extract/kg feed with 40 ml ZZ/kg feed (SF60/ZZ40), SF50/ZZ50, BP90/SF10, and BP50/SF50-were mixed with a commercial diet and used in both treatment and prevention trials. Haematological and immunological parameters were performed every week for four weeks. Results: In prevention trials, tilapia fed SF50/ZZ50 showed a significant increase of white and red blood cells from weeks 2 to 4. Similarly, significantly increased haematocrit was also found in tilapia fed SF50/ZZ50 in the treatment trial but not in the prevention trial. However, haemoglobin of tilapia in both trials was not affected by any of the various combinations of extract in the diet. Furthermore, phagocytic, respiratory burst, lysozyme activity indexes and survival rate of fish fed with combined extracts were found to be significantly higher than controls. Moreover, the amount of pathogenic bacteria in fish that were fed combined extracts was also lower than the control and was significantly different at week 4. Conclusions: This study indicates that the addition of combined extract into feed has a positive effect on the tilapia's immune system. The SF50/ZZ50 combination appears to improve the innate immune system of tilapia to treat and prevent bacterial infections.