Four successive cases of human fasciolosis in Japan

Fasciolosis is a food-borne parasitic disease, caused by the large liver fluke, Fasciola. Humans acquire infection by ingesting fresh or undercooked water plants, on which infective metacercaria encyst. In spite of the rarity of the disease in Japan, we encountered four successive fasciolosis patients within a short period, who were all living in the same area. The patients were 70-82 years old, three females and the husband of one of the female patients. They started complaining of non-specific symptoms, such as fever, general fatigue, appetite loss, and abdominal pain, almost at the same time. All patients showed prominent peripheral blood eosinophilia, and the medical imaging indicated multiple hepatic lesions. No parasite eggs or worms were detected in any of the patients. Diagnosis was made serologically and they were treated with praziquantel and/or triclabendazole. No cattle or sheep were farmed in the area, but the wild sika deer, Cervus nippon, inhabited adjacent to the residential area. The intermediate host snail, Austropeplea ollula, were found near the residence of the patients, and one of the collected snails was positive for F. hepatica/gigantica hybrid type rediae. Our report should alarm the medical professionals for this rare and unfamiliar parasitic disease.