ABSTRACT
I. BACKGROUND Opisthorchis viverrini is one of a number of flukes that infect the human biliary system. It is closely related to O. felineus and Clonorchis sinensis. This parasite was first found at autopsies of two prisoners from northern Thailand in 1912 (1). It was thought to be O. felineus until an epidemiological survey was conducted in Thailand by Sadun, who recognized the difference between O. felineus and the liver fluke found in Thailand and reported this in 1955 (2). O. viverrini infects millions of people in the northeastern and northern parts of Thailand (3), and most of the clinical studies of this disease were performed during the 1980s and 1990s.
