In 2013, four cases of digenean infection occurred among 0-year Seriola dumerili, imported from China and subsequently cultured in Kagoshima Prefecture, Japan. In each case, a single immature worm was recovered from the abdominal cavity, kidney, or skeletal muscle, associated with black viscous substances, probably of parasite origin, suggesting that the parasite was migrating within the fish body. From morphological and molecular analyses, the digenean was identified as Hirudinella ventricosa. No such infection was recorded among 1,968 cultured Seriola spp. examined in Kagoshima during 2012–2018 except for the four cases. In 2017, black to brown substances were noticed in the fillets of Seriola quinqueradiata at a processing factory. The fish with contamination had been cultured for two years from wild seeds caught along the coast of Kagoshima Prefecture. No worm was found, but the 28S rRNA gene sequence analysis demonstrated that they were originated from H. ventricosa. Both the infection of S. dumerili and the contaminated fillets of S. quinqueradiata are assumed to be the cases of larva migrans caused by the hirudinellid digenean.
