Abstract
Dactylogyrus sp. (Monogenea) is one of the most dangerous pathogens causing parasitic infections in carp (Cyprinus carpio) and other freshwater fish. Due to the adverse effects of conventional chemical treatments on the environment and fish, the use of herbal products in aquaculture against various diseases has increased. In the present study, anthelmintic effects of peppermint (Mentha piperita), lemon (Citrus limon), and tea tree (Melaleuca alternifolia) essential oils against Dactylogyrus sp. found on the gills of carp were studied using in vitro and in vivo experiments. In in vitro experiments, 1, 2.5, 5, and 10 μl/ml concentrations of these essential oils were tested on the parasites and cumulative mortalities were observed to reach 100 % after treatment with peppermint, lemon, and tea tree essential oils of 1 μl/ml concentration in approximately 15, 10 and 2 min, respectively. The in vitro experiments demonstrated that the cumulative mortality of the parasites increased with essential oil concentration and exposure duration. As the concentration of essential oil used increased, the observed mean time to death of parasites decreased. In in vivo experiments, median effective concentrations (EC50) as assessed by in vitro tests for peppermint and lemon essential oils in 5 min exposure and EC50 concentration for tea tree essential oil in 2 min exposure was applied on fish as a single bath and there was a significant decrease in the mean parasite intensities (p<0.05). Antiparasitic efficacies of peppermint, lemon, and tea tree essential oils were determined as 28.23 %, 30.95 %, and 35.31 %, respectively. The tea tree oil was the most effective and peppermint oil was the least effective in both in vitro and in vivo experiments. All three herbal essential oils tested in this study have weak antiparasitic potential against monogenean infections in fish.