This study revealed the infection status of P. parva with the metacercariae of M. orientalis in the Sunam stream of the Nakdong River, a well-known focus of Clonorchis sinensis. A total of 60 P. parva were divided into 4 groups by the size (80-90, 70-79, 60-69 and 50-59 mm) and were digested by pepsin-HCl solution in a 36 degrees C incubator. The metacercariae of M. orientalis were collected and counted under a stereomicroscope. A total of 3,885 metacercariae were found, and average number/fish in each group were 143, 54, 23 and 40. They were 175.3 x 155.4 microns in average size and had thick cyst wall(13.1 microns in average). By the results, it is proved that the life cycle of M. orientalis is actively maintained in the Sunam stream of the Nakdong River.
