An epidemiologic study on clonorchiasis and metagonimiasis in riverside areas in Korea

A study was carried out to figure the cases and to observe the endemic status of clonorchiasis and metagonimiasis in endemic areas in Korea. Total 13,373 inhabitants living in 40 villages along 7 main rivers and 9 small streams were subjected to stool examination. They were selected randomly among the riverside population. Their specimens were examined both by cellphane thick smear method and Stoll's egg countung technique. This study was performed during the period from May 1979 to April 1980. The results obtained are as follows: 1. The egg positive rate of any kind of helminths was 58.7% out of 13,373 examned cases, and the egg positive rates by each helminth were; Clonorchis sinensis 21.5%, Metagonimus yokogaqai 4.8%, large type Metagonimus eggs 0.4%, Ascaris lumbricoides 22.9%, Trichuris trichiura 35.2%, hookworm 0.2%, Taenia sp. 0.5%, Hymenolepis nana 0.07%, Paragonimus westermani 2 cases, Fasciola sp. 4 cases, Echinostoma sp. 1 case and Hymenolepis diminuta 1 case respectively. 2. Many endemic foci of clonorchiasis were revealed along the 7 major rivers. The egg positive rates of each river basin differed from each other significantly; Nagdonggang 40.2%, Yeongsangang 30.8%, Seomjingang 17.3%, Hangang 15.7%, Tamjingang 15.9%, Geumgang 12.0% and Mangyeonggang 8.0%. The cases of clonorchiasis were estimated in range 830,000 to 890,000 in riverside areas of the 7 rivers. By grading the infection intensity, 64.7% was in Grade I(EPG 0-900), 28.6% in Grade II (EPG 1000-9,900), 5.5% in Grade III (EPG 10,000-29,900) and 1.3% in Grade IV (EPG over 30,000). The proportion of the cases in Grade III and IV was 6.8% among positive cases. Therefore 60,000 cases at least were regarded to suffer from it clinically. Males of 30-60 years of age showed higher positive rate and heavier burden of infection. This makes clonorchiasis more important socially because the patients lose their social productivity. 3. A few endemic foci of metagonimiasis were detected newly by egg detection; Samcheong 28.5% egg positive rate, Uljin 21.3%, Yeuongdeog 46.3%, Milyang 6.7%, Yeongil 9.2% and Geoje 18.2%. The mean EPG values were in range of 320-7, 120 by the focus. The egg positive rate and proportion of EPG Grade varied greatly by the area, and mean proportion of the positive cases were 69.7% in Grade I, 24.1% in Grade II, 5.0% in Grade III and 1.2% in Grade IV. Males of 30-60 years were infected in higher rate also. The large sized eggs of Metagonimus were found also in upper basin of Hangang and Geumgang mainly. They were regarded as eggs of M. takahashii which is mediated by the cyprinid fishes. Its significance should be studied further. Clonorchiasis and metagonimiasis should be realized as important public health problems in Korea by their wide distribution, high prevalence rate and heavy infection intensity. Comprehensive measures against them are needed urgently.