Assessment of the Immune Status in Nile Tilapia (Oreochromis niloticus) Experimentally Challenged with Toxogenic / Septicemic Bacteria During Treatment Trial with Florfenicol and Enrofloxacin

Limiting factors to the tilapia farming industry are numerous and deeply embedded in th e environmental paradigm. Infectious diseases are moved to the top list of limiting factors that harshly endangering the fish health with consequent negative impact on the entire population ecology. Antibiotic selection is of major time-wise and economical importance when an episode of bacterial infection has swiftly attacked certain cultured fish population. In the current study an in-vitro microcosm system has been established to assess the efficacy of two major broad spectrum antibiotics against two septicemic / saprophytic fish pathogens affecting Nile tilapia (Oreochromis niloticus). The antibiogram as well as histopatholog ical examination of the tissue sections of the challenged tilapias have indicated that Florfenicol is more effective than Enrofloxacin in combating Clostridium perfringens infection. However, Enrofloxacin has proved a superior efficacy against pseudomonas infections. Both antibiotics have regulated the nitric oxide / nitric oxide intermediates with an ultimate neutralization of the damage associated with oxidative stresses. Further, the two antibiotics were able to modulate the innate humoral immune responses of the challenged fish. Analysis of the water quality measures of the challenged fish aquaria has revealed a relative increase in water pH and ammonia concentrations in Clostridium perfringens as well as Pseudomonas florescence challenged aquaria. As a positive indicator, ammonia and pH concentration were markedly decreased in both Florfenicol and Enrofloxacin treated aquaria. However, it is worthy to mention that ammonia and pH concentration s wer e sharply decreased in Florfenicol than Enrofloxacin treated fish aquaria. In conclusion, we recommend that antibiotic of choice can be effectively used not only to treat fish but also to modulate their immune response as well as improve the surrounding environmental water parameters.