• Journal of fish pathology
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• v.36 no.2
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• pp.293-302
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• 2023

This study evaluated the acute toxicity induced by oxolinic acid (OA), neomycin-oxytetracycline combination (NEO-OTC) and florfenicol (FF) administered to guppy (Poecilia reticulata) by comparing standard formulations with commercial preparations (COOaqua curinpotion, COOaqua terafinpotion and COOaqua profenpotion, respectively) for ornamental fish at concentrations of 2-4%. NEO-OTC exhibited the highest acute toxicity in guppy, with no difference observed between the pstandard formulation and commercial preparation (LC₅₀ = 126.08 mg/L and 112.44 mg/L, respectively). OA acute toxicity was assessed in the form of sodium salt, with an LC₅₀ of 504.61 mg/L for the standard formulation and a slightly increased toxicity of 316.11 mg/L for the commercial preparation. In contrast, no mortality was observed during the 96-hour exposure period with the standard formulation in the form of oxolinic acid. The acute toxicity of FF was measured to be above 1,000 mg/L for the standard formulation; however, the commercial preparation significantly increased to 158.53 mg/L. These results indicate that toxicity can significantly increase in commercial formulations, especially those with low levels of active ingredients. This is presumed to be attributed to the organic solvents or solubilizing agents present in the commercial preparations, which may enhance toxicity. Additionally, guppy infected with Aeromonas salmonicida were effectively protected against mortality by administering OA, NEO-OTC and FF at concentrations of 50 mg/L, 100 mg/L and 15 mg/L, respectively, for 2 hours and at half the dose for 24 hours. This result indicates that liquid formulations containing low concentrations of antibiotics may partially increase toxicity, but there is no problem in effectively treating diseases in ornamental fish.