Treatment of vibriosis in European sea bass larvae, Dicentrarchus labrax L., with oxolinic acid administered by bath or through medicated nauplii of Artemia franciscana (Kellogg): efficacy and residual kinetics

European sea bass larvae were challenged by bath with Listonella anguillarum strain 332A, 2.5 × 107 CFU mL−1 for 1 h. Fish either received no treatment or oral treatment with Artemia franciscana (Kellog) nauplii enriched with oxolinic acid, or bath treatments with oxolinic acid. Medication commenced 1 day following challenge and was performed on days 1, 3 and 5 post-challenge at a dosage of 20 mg L−1 for 2 h for bath treatments, while two doses each of 750 nauplii per fish were administered daily for five consecutive days in oral treatments. Cumulative mortality reached 96% for the unmedicated challenged group, 32% in the group receiving bath treatments and 17% in the group receiving medicated nauplii. Pharmacokinetic parameters of oxolinic acid were calculated in sea bass larvae, for both treatments. Steady-state concentrations of oxolinic acid of 48.0 and 75.2 μg g−1 were achieved for bath treatment and oral treatment, respectively, while the elimination half-life was calculated to be 25.1 h for bath treatment and 21.7 h for oral treatment.