Occurrence of the Myxosporean Emaciation Disease Caused by Enteromyxum leei in Cultured Japanese Flounder Paralichthys olivaceus

The myxosporean emaciation disease has been recently found in Japanese flounder Paralichthys olivaceus cultured in land-based tanks in Miyazaki Prefecture, Japan. Affected fish showed external signs of distended abdomen, rectal prolapse, sunken eyes and a typical bony ridge on the skull. Parasitological and histopathological examinations revealed that the developmental stages of Enteromyxum Ieei parasitized the intestinal epithelium of diseased fish. No other enteric myxozoans were observed in the affected fish. A molecular analysis of SSU rDNA confirmed that the causative myxozoan was identified as E. leei. Experimental transmission of E. leei was achieved to naive Japanese flounder and tiger puffer Takifugu rubripes by feeding with gut tissues taken from infected Japanese flounder. The present study indicates that the myxosporean emaciation disease of Japanese flounder is caused by E. leei.