Efficacy of Oxolinic Acid Against Aeromonas hydrophila Infection in Nile tilapia Oreochromis niloticus Juveniles

Oxolinic acid (OA), a broad-spectrum quinolone antibiotic that plays a crucial role in human medicine, is often used in aquaculture as a second-line treatment at 12 mg/kg biomass/day continuously for seven days. The objective of this study was to assess its effectiveness against Aeromonas hydrophila infection in Nile tilapia Oreochromis niloticus in terms of progression and healing of wounds, clinical biochemistry and histopathological changes upon challenge and treatment. To evaluate the efficacy, the juveniles were intramuscularly challenged with A. hydrophila at a sublethal dose of 1.93×106 cells/fish, followed by the administration of OA-supplemented feed at 2% body weight daily for seven days. OA treatment yielded better consequences in terms of increased feed intake and biomass and decreased plasma biochemical parameters, histopathological changes and improved recovery from A. hydrophila infection compared to the untreated group. Wounds of the OA-treated group healed at a faster rate, with complete healing within 12 days post-injection, while the wounds of the untreated group took longer to heal. Though the efficacy of OA against A. hydrophila infection in tilapia was established in this study, it is important to exercise caution regarding its application in aquaculture due to its classification as a critically important medicine for humans.