Clonorchis sinensis: life cycle, intermediate hosts, transmission to man and geographical distribution in Korea.

The snail host of Clonorchis sinensis in Korea is referred to as Parafossarulus manchouricus, but it has been recorded also as Bulimus striatulus japonicus in literature published up to late 1950. The specific name of the snail was corrected such that Bulimus striatulus of China, Japan, and Korea should be incorporated in the species of P. manchouricus. In general, the snail exists in limited areas of the rivers Han, Kum, Mankyung, Naktong, and Yeongsan, and the infestation of the snail with the cercaria of C. sinensis is very low. In recent years, ten species of small fresh-water fish are known as second intermediate hosts of the fluke. Of these, the southern top-mouthed minnow, Pseudorasbora parva, was most heavily infected. The striped shiner, Pungtungia herzi, Korean shiner, Gnathopogon atromaculatus, gudgeon, Pseudogobio esocinus, oily shiner, Sarcocheilichthys sinensis, and Korean barbel, Hemibarbus labeo, were infected intermediately. Whereas, the flat bitterling, Paracheilognathus rhombea, oily bitterling, Acheilognathus limbata, and Korean rose bitterling, Acanthorhodeus taenianalis were infected with a few cysts. No infections were found in the pale chub, Zacco platypus, crussian carp, Carassius carassius, and carp, Cyprinus carpio. Most Koreans are usually infected by eating slices of raw fresh-water fish coated with hot bean paste. Raw fish is a common accompaniment in drinking the rice wine "Marcgulee" in rural communities and a health food for males. Numerous epidemiological studies revealed that the prevalence rate for the fluke among the residents in the vicinity of rivers is higher than those in the areas far from the rivers. The rate is higher among males than females and increases with age.