ABSTRACT
The prevalence of C. sinensis infection along the Nam river, Korea, was 38.7% of 5,291 people examined. Prevalence rates varied from 42% at the upper stream to 34% at the middle stream and 40% at the down stream region. Rates were highest (53.4-54.3%) in the 30-59 years of age group. The positive rates in primary school chidren, school students, teachers and local officers, and other inhabitants were 16.5%, 22.6%, 46.2% and 49.6% respectively. 53.6% of cases were light infected, i.e. less than 4,000/EPG. The cercarial expulsion rate of 5,005 Parafossarulus sp. was 0.34%. Snails naturally infected with C. sinensis expelled about 788 cercariae/day. Ten of 18 species of freshwater fish examined had C. sinensis metacercariae. To prevent clonorchiasis in the endemic areas, the effective health education system is suggested as a control measure. [retyped from English summary]