Efficacy of orally administered flumequine in the treatment of vibriosis caused by Listonella anguillarum in Atlantic cod Gadus morhua

The efficacy of orally administered flumequine in the treatment of experimentally induced vibriosis in Atlantic cod Gadus morhua was investigated. Cod (mean ± SD, 120 ± 30 g) were randomly distributed to twelve tanks and bath challenged for 1 h with Listonella anguillarum serotype O2α, strain HI-610, using a dose of 9.2 × 106 CFU ml–1. At 3 d post-challenge, medication was introduced in 10 of the groups at doses of 2.5, 5, 10, 15 and 25 mg flumequine kg–1 body weight d–1 in duplicate. The medication was administered on Days 1, 2, 4, 6, 8, and 10 after the initiation of treatment. In challenged unmedicated fish, mortality started on Day 4 post-challenge, reaching a final cumulative mortality of 82% at Day 18. In the medicated groups, mortality started on Days 3 to 5 post-challenge, reaching final cumulative mortalities of 42, 49, 37, 37 and 23% respectively for the fish treated with 2.5, 5, 10, 15 and 25 mg flumequine kg–1 body weight d–1. Survival of medicated fish in all groups was significantly greater than in challenged unmedicated fish (p < 0.001). Twenty-four h following the final medication, HPLC analysis found a linear relationship between doses and mean concentrations of the drug in plasma, muscle and liver