Anthelmintic Efficacy of Palmarosa Oil and Curcuma Oil against the Fish Ectoparasite Gyrodactylus kobayashii (monogenean)

SIMPLE SUMMARY: Aquaculture is an important source of animal protein. However, in recent years, with an intensification of farming, the risk of infectious diseases is increasing, especially the diseases caused by monogeneans, resulting in huge economic losses to aquaculture. Currently, the prevention and control of monogenean in fish mainly rely on some chemical drugs, such as formaldehyde, rotenone, and praziquantel. However, prolonged and frequent use of these chemicals leads to the occurrence of drug resistance, some adverse environmental impacts, and even contamination of fish products with drug residues. Therefore, it is urgent to develop efficient and environment-friendly drugs for the control of monogeneans in aquaculture. Natural plant-derived medicines are one of the alternative options. Therefore, in this study, anthelmintic efficacy of various essential oils was evaluated. The results indicated that palmarosa oil and curcuma oil showed potent anthelmintic activity against monogenean, and curcuma oil also had an anesthetic effect on monogenean. Moreover, these two essential oils displayed a high safety for fish. Therefore, palmarosa oil and curcuma oil could be viable alternatives for the prevention and control of monogenean infection in aquaculture. ABSTRACT: Monogeneans are a serious threat to the development of aquaculture due to the severe economic losses they cause. The prevention and treatment of this disease are increasingly difficult because of the environmental and health concerns caused by the use of chemical anthelmintics and the emergence of drug resistance. It is thus necessary to search for effective alternatives for the treatment of monogenean infections. In the current study, anthelmintic efficacy of 16 selected essential oils (EOs) was investigated using the goldfish (Carassius auratus)–Gyrodactylus kobayashii model. The screening experiment indicated that palmarosa oil and curcuma oil had satisfactory anthelmintic activity against G. kobayashii with EC(100) values of 10 and 12 mg/L after 24-h exposure, respectively. The in vivo and in vitro assays indicated anthelmintic efficacy of palmarosa oil against G. kobayashii was in a time and dose-dependent manner. Interestingly, curcuma oil showed an anesthetic effect on G. kobayashii, and its anthelmintic activity was dose-dependent rather than time-dependent in the concentration range tested in this study. Additionally, the 24-h LC(50) (50% lethal concentration) against goldfish of these two EOs was 8.19-fold and 5.54-fold higher than their corresponding EC(50) (50% effective concentration) against G. kobayashii, respectively. Moreover, exposure to these two EOs at 100% effective concentration against G. kobayashii had no serious physiological and histopathological influence on goldfish. These results demonstrated a high safety for goldfish of these two EOs. Overall, palmarosa oil and curcuma oil could be potential candidates for the treatment of G. kobayashii infections in aquaculture.