Naringenin as a Promising Therapeutic Agent for <i>Gyrodactylus kobayashii</i> in Goldfish

Gyrodactylus spp. pose significant threats to farmed fish due to their high pathogenicity, resulting in substantial economic losses in aquaculture. Currently, treatments for gyrodactylosis primarily rely on chemical agents, the efficacy and safety of which are not always satisfactory, underscoring the urgent need for novel anthelmintic agents. In the pursuit of novel therapeutic agents, we assessed the in vivo anthelmintic efficacy of 20 natural compounds using a goldfish (Carassius auratus)-Gyrodactylus kobayashii infection model. Among these compounds, naringenin (NAR) exhibited the highest efficacy and was selected for further investigation. In vitro results demonstrated NAR's significant anti-parasitic activity, achieving 100% mortality at 4.0 mg/L after 60 min of exposure. Subsequent in vivo investigations revealed that the median effective concentration (EC₅₀) of NAR was 0.859 mg/L at 24 h and 0.704 mg/L at 48 h post-treatment, with EC₁₀₀ at 2 mg/L. Additionally, NAR significantly impaired the mobility of G. kobayashii. Confocal microscopy revealed that NAR-induced structural damage in worm tissues, including epidermal disruption and muscle dissolution. Moreover, both in vitro and in vivo exposure to NAR caused a decline in ATP levels, indicating potential impairment of energy production in G. kobayashii. Collectively, these findings establish NAR as a promising therapeutic agent for protecting farmed fish against Gyrodactylus infections.