Synergy of herbal ingredients combination against Dactylogyrus spp. in an infected goldfish model for monogenean management

• First study investigates synergy of two herbs to control parasites in aquaculture.
• Both extract and compound combinations are effective to eliminate Dactylogyrus.
• Strong synergies are observed in both extract and compound combinations of two herbs.
• The toxicity of compound pairs is lower than Gracillin (GR) alone.

Current chemotherapy of mono-component for Dactylogyrus is unsatisfactory due to its limited efficacy with side effects including pesticide resistance and drug residue. The present study is conducted to investigate the effects of herbal ingredients combination against Dactylogyrus on Carassius auratus under in vivo conditions. The ingredients of Dioscorea zingiberensis (D. zingiberensis) and Ginkgo biloba (G. biloba) are administered individually and in combination in an experimental fish infection model in this study. Finally, strong synergy actions are observed in both the methanol extract combinations and the active compound combinations between D. zingiberensis and G. biloba. The anthelmintic effects of the combination are expressed in terms of the values of EC50, EC75, EC90, and EC99 to compare with the phytomedicine alone. The combination index (CI) is also calculated by using the combination index algorithm. Both the values of effective concentration and combination index indicate a highly synergistic anthelmintic effect against Dactylogyrus. Our study provides a powerful means by which anthelmintic combination therapies can be examined and demonstrates that the combinations of herbal ingredients have excellent properties and are predicted to give improved cure rates in monogenean management of aquaculture.