Efficacy of Febantel Against Gill Monogeneans of Amberjacks I: Laboratory Assessment for Effective Dose and Administration Period

Three experimental trials were conducted to determine the effective dose and administration period of a pro-benzimidazole anthelmintic drug febantel (FBT) against two gill monogenean species on amberjacks; Zeuxapta japonica on Seriola dumerili and Heteraxine heterocerca on Seriola quinqueradiata. ​The mean Z. japonica intensities were checked at 3 days after given FBT-coated feeds at the doses of 1, 5, 10, or 20 mg/kg body weight (BW)/day (d) for 5 consecutive days (trial 1), and 10 mg/kg BW/d for 1, 3, or 5 days (trial 2). ​Based on the results of these trials, the efficacy of oral FBT treatment was assessed for H. heterocerca infections at the treatment regime of 10 mg/kg BW/d for 3 or 5 days (trial 3). ​Over 95% FBT efficacies were achieved for both monogenean species when the fish received the dose of 10 mg/kg/d or higher for 5 consecutive days. ​Amberjacks showed no apparent avoidance to the FBT-coated feed and no apparent signs of the drug toxicity were detected. ​Our results demonstrated that the in-feed FBT treatment at the dose of 10 mg/kg BW/d for 5 days is an effective, easy, and practical control measure against gill monogenean infections in aquaculture of Seriola fish.