Viable metacercariae of Opisthorchis viverrini in northeastern Thai cyprinid fish dishes--as part of a rational program for control of O. viverrini-associated cholangiocarcinoma.

Among the various types of chronic helminthic infections, only schistosomiasis hematobium, opisthorchiasis, and clonorchiasis in a long-standing inflammation are found to be causative agents of cancer. Opisthorchiasis and Opisthorchis viverrini-associated bile duct cancer are prevalent among the residents in northeastern Thailand, who prefer consuming raw or improperly cooked cyprinid fish. Although numerous studies have reported on the presence of O. viverrini metacercariae in freshwater cyprinid fishes, none of the data has been derived directly from cyprinid fish dishes. Here, we have demonstrated the presence of viable metacercariae in a number of cyprinid fish dishes that are among the favorite foods of northeastern Thais. Traditional salt-fermented and grilled cyprinid fish were found to be safe to consume, but not raw fish salad or cyprinid fish fermented in sticky rice for 69 h. This information could be used as part of a rational and sustainable control program for O. viverrini-associated bile duct cancer.