Field Trials of Febantel for the Treatment of the Beko Disease in <i>Seriola</i> spp.

Abstract

Outbreaks of beko disease caused by the microsporidian Microsporidium seriolae have been a serious problem in Seriola aquaculture in Japan. Recent laboratory experiments demonstrated that the oral administration of a probenzimidazole febantel (FBT) at the early stage of infection effectively suppresses the formation of the microsporidian cysts in the trunk muscle. This opens the possibility of drug therapy for the beko disease. Here, we conduct a series of field trials to assess the efficacy and practicality of FBT treatment for beko disease in farmed Seriola quinqueradiata and Seriola dumerili. The trial tested FBT doses of 0, 1, 3, 5, and 10 mg/kg bw for 5 days resulted in significantly lower beko disease-related mortality, cyst detection rate, and progression of cyst formation in the 10 mg/kg group of S. quinqueradiata. This 10 mg/kg bw for 5 days FBT administration was also effective to suppress cyst formation in S. dumerili. Another trial used fifteen repeated administrations of 10 mg/kg FBT for 5 days with 2 days interval in between completely prevented the cyst formation in juvenile S. quinqueradiata, in comparison to the cyst detection rate of as high as 83.3% in non-drug treated fish. No adverse effects of FBT on the fish were observed in any of the trials. Our field trials indicate that the oral administration of FBT at the dose of 10 mg/kg bw is highly effective and practical chemotherapy for beko disease in Seriola fish.

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

“…The FBT treatment at the same dose (10 mg/kg BW/d for 5 days) has been shown to be safe in Seriola spp. in other studies (Kawakami et al, 2021;Shirakashi et al, 2021aShirakashi et al, , 2021b. Therefore, this treatment regimen likely induces no or very minor, if any, toxicity to S. dumerili and S. quinqueradiata.…”

“…However, the efficacy was reduced to 70.8% when the dose 75 mg/kg was given for 6 days via surface coated feed, likely due to palatability problem (Williams et al, 2007). In contrast, Seriola fish did not avoid FBT, even in surface coated feed, and this can be a major merit for the practical use of the drug (Kawakami et al, 2021). Toxicity of FBT, however, can be an issue.…”

“…This drug has broad anti-parasitic spectrum against nematodes, cestodes, and some trematodes (Dar et al, 2017;Hardy-Smith et al, 2012). Moreover, the high efficacy of FBT against a microsporidian Microsporidium seriolae, the causative agent of beko disease, has recently been demonstrated in Seriola fish (Yanagi et al, 2021). Since both S. dumerili and S. quinqueradiata show no apparent avoidance to FBT (Kawakami et al, 2021), it can be used as a convenient in-feed drug, and thus, it has a potential to be an easy and non-stressful treatment option against the gill monogeneans.…”

“…Moreover, the high efficacy of FBT against a microsporidian Microsporidium seriolae, the causative agent of beko disease, has recently been demonstrated in Seriola fish (Yanagi et al, 2021). Since both S. dumerili and S. quinqueradiata show no apparent avoidance to FBT (Kawakami et al, 2021), it can be used as a convenient in-feed drug, and thus, it has a potential to be an easy and non-stressful treatment option against the gill monogeneans. In the present study, we aim to determine the appropriate dose and administration period of oral FBT treatment against H. heterocerca and Z. japonica in Seriola spp.…”

Evaluations of Lethal and Sub-lethal Toxicity of Febantel in the Juvenile Japanese Amberjack <i>Seriola quinqueradiata</i>

“…No adverse effects (abnormal behavior, reduced growth, and/or mortality) of FBZ or FBT were found in rainbow trout Oncorhynchus mykiss (exposure: 12.5 mg/L for 60 min) (Tojo et al, 1992), silver perch, Bidyanus bidyanus (exposure: 10 mg/L for 48 h; oral: 75 mg/kg/d for 6 days) (Forwood et al, 2013), zebrafish, Danio rerio (exposure: 25 μg/mL twice a day for 3 days) (Samaee, 2015), or in tiger puffer, T. rubripes (oral: 12.5, 25, or 50 mg/kg/d for 5, 5, and 3 days, respectively) (Kimura et al, 2006). Moreover, no signs of FBT toxicity was observed in S. quinqueradiata and S. dumerili that received the oral dose of 25 mg/kg/d for 5 days, or repeatedly administrated with 10 mg/kg/d FBT for 5 days for fifteen times (Kawakami et al, 2021;. In contrast, adverse effects of other benzimidazole, such as albendazole or mebendazole, have been reported in fish (Athanassopoulou et al, 2009;Fuhr et al, 2012;Nwani et al, 2016;Samaee, 2015).…”