Chemical Treatment of Beko Disease in Seriola Fishes: Laboratory Trials of Commercially Available Fishery and Veterinary Medicines

Abstract

Beko disease, caused by infection of the microsporidian Microsporidium seriolae, results in significant damage to farmed amberjack, Seriola spp., in Japan. ​Little is known about the disease, including the general biology of the causative agent, and no therapeutic method has been established to treat it. ​We determine the therapeutic efficacies of various drugs by administering them in-feed to juvenile Seriola spp. naturally infected with M. seriolae. ​Candidate drugs include commercially available fishery anthelminthic, febantel, and eight other compounds. ​Fish were given various doses of drugs, and M. seriolae infection in their trunk muscle was then checked by quantitative PCR (qPCR) and macroscopic cyst detection. ​Fish treated with febantel at an early stage of infection had significantly lower rates of cyst formation and qPCR-positive. ​However, febantel administered to fish after cyst formation did not reduce cyst numbers. ​Other drugs showed no apparent efficacy to prevent cyst formation or to promote cyst reduction. ​Results indicate febantel is a promising therapeutic agent for beko disease when applied at an early stage of infection.