Therapeutic Effect of Flumequine against Pseudotuberculosis in Cultured Yellowtail

The in vitro antibacterial activity of flumequine, a synthetic quinolone antibacterial agent, against Pasteurella piscicida, which causes pseudotuberculosis in yellowtail Seriola quinqueradiata was examined. Subsequently, the in vivo effective dose of the agent and its therapeutic effect in the field were studied. Flumequine showed an minimum inhibitory concentration of 0.1-0.39μg/ml against 43 strains of P. piscicida out of 44 strains tested. In examining the in vivo effective dose, 5, 10, 15 and 20mg/kg body weight/day of flumequine were administered for 5 days to diseased yellowtail naturally infected with pesudotuberculosis. After completion of administration, the number of dead fish in the group dosed with 20mg/kg was significantly lower than in other groups. Further, 10 and 20mg/kg of flumequine were administer-ed for 5 days, in the field, to diseased yellowtail with pesudotuberculosis. It was found that the numbers of dead fish in the groups administered with flumequine were lower than that in the control group, and that mortalities in the group dosed with 20mg/kg were particularly low.