Evaluation of treatment efficacy of doxycycline and albendazole against scuticociliatosis in olive flounder (Paralichthys olivaceus)

Abstract

Scuticociliatosis is a leading cause of mass mortality in cultured olive flounder (Paralichthys olivaceus) in Korea. However, still no effective treatment measures have been developed. In the present study, we selected two drugs, doxycycline and albendazole, that were demonstrated to have high in vitro scuticocidal activity and possess ability to cross blood–brain barrier (BBB), and evaluated their treatment efficacy against scuticociliatosis caused by Miamiensis avidus in olive flounder. In both oral and bath treatment experiments, groups of fish fed a diet containing doxycycline or bathed with freshwater containing doxycycline showed clearly higher survival rates than control groups. Although the groups of fish fed a diet containing albendazole or bathed with freshwater containing albendazole showed higher survival rates than the control group, the rates were greatly lower than those of the groups treated with doxycycline. Poor intestinal absorption, low solubility in water, and low lipophilicity of albendazole were considered as the possible cause of the low efficacy. In conclusion, the present results suggest that doxycycline can be used to treat systemic scuticociliatosis in olive flounder through oral administration and bath.