Recent results of mass stool examination for parasitic infections revealed 0.01-0.0001 percent of Paragonimus egg positive rate in Seoul school-children. This survey was carried out to understand the infection status of intermediate hosts and their relations to human paragonimiasis in Seoul. Twelve mountainous streams in the outskirts of Seoul were surveyed. From all streams, Semisulcospira libertina, the snail intermediate host was not detected. From 7 streams 132 crayfishes, Cambaroides similis, the second intermediate host were collected. From them no metacercaria was found. The results indicated that crayfish in district of Seoul is no more an infection source of paragonimiasis. Possible factors related with the ecology of intermediate hosts were briefly discussed from the epidemiological view point.
parasitology-helminth-trematoda ; Paragonimus westermani ; host ; Semisulcospira libertina ; Cambaroides similis

Studies of the water analysis of the breeding place of the first intermediate host(Semisulcospira libertina) was carried out. The breeding place of Semisulcospira libertina in the Haenam area were found mainly in pebbly and sandy riverbed of the upper stream and halfway up the Donghae river, but we could not find the habitats of Semisulcospira libertina in the spring, paddyfield and tidal part of flow in which the content of Cl ion, Ca ion, total alkalinity, total hardness and pH were obviously higher than those of the breeding place. The range of physical and chemical characters of the Semisulcospira libertina breeding water were as follows. 0.05-0.7 m/s of optimal flowing velocity of fresh water, 20-50 cm in depth, 7.12+/-0.17 of optimal pH range 19.4+/-4.92(mg/l)in total alkalinity, 9.4+/-2.97(mg/l) of Ca ion, 9.8+/-2.3(mg/l) of Cl ion content, 115.1+/-34.2(mg/l) of total hardness, but there were no remarkable differences between the habitat water and the contrasts in their specific gravities. In the comparison of analytical result of the breeding water at Haenam, the content of Ca ion, Cl ion, total alkalinity, total hardness and pH showed a gradually higher value in the lower reaches of the river than those of the upper stream and halfway up the river.
parasitology-snail-intermediate host ; Semisulcospira libertina ; breeding place

The question of infectivity and prevalence of Clonorchis sinensis in Cheju province (Quelpart Island) was arisen to authors since the several surveys on the endemic diseases were performed in this island. Therefore, authors decided to solute this question. Then the survey on the possible second intermediate host of Clonorchis sinensis was performed and reported already with negative finding. At present time, authors carried out the collection of all kinds of fresh-water snails through all areas of this island, to confirm the presence or not of Parafossarulus manchouricus, the only first intermediate host of Clonorchis sinensis in Korea . And the following results were obtained. The fresh-water snails collected in the survey were Semisulcospira libertina Gould and Lymnaea ollula Gould. Parafossarulus manchouricus Bourguigant was not collected in this island. It is confirmed that the Clonorchis sinensis can not be prevalent in this island.
parasitology-helminth-trematoda-Clonorchis sinensis ; life cycle ; epidemology ; Parafossarulus manchouricus ; Semisulcospira libertina Gould ; Lymnaea ollula Gould

The Jinyang Lake is dammed up Nam River, and surrounded by Jinju city and four counties; Jinyang, Sanchong, Hadong, and Sachon in Kyongsang-Nam-Do, Korea. The area around this man-made lake have been known as an endemic focus of clonorchiasis in Korea. The present study was first aimed to know the distribution of freshwater mollusks including medically important snails, and larval trematodes shed from Parafossarulus manchouricus and Semisulcospira libertina. In addtion to above studies, water analyses in each snail habitat were carried out in order to figure out a part of their environmental factors. This malaco-ecological survey was done at the six areas around upper, middle and lower parts of the lake for 4 months, August-November, 1983. Total nine species of freshwater mollusks were collected throughout the study: 4 species of gastropods; Semisulcospira libertina, Cipangopaludina chinensis, Parafossarulus manchouricus and Radix auricularia, and 5 species of bivalves; Unio douglasiae, Anodonta woodiana, Lamprotula gottschei, Corbicula fluminea and Limnoperma lucustris. Out of nine species of freshwater mollusks, three species of gastropods; S. libertina, P. manchouricus and R. auricularia were medically important in terms of the transmission of digenetic trematodes to humans. P. manchouricus and R. auricularia were mainly collected from the shallow ponds and the irrigation channels with the muddy basin, but S. libertina and the bivalves were only collected from the stream of Nam river where the gravels and rocks were dominant. The levels of dissolved oxygen(D.O.) and biochemical oxygen demand (B.O.D.(5)) of the water specimens sampled from the study areas ranged from 6.0 to 9.6 ppm and from 0.4 to 1.6 ppm respectively. As a result, it is considered that water system around the Jinyang Lake might be relatively clean without any heavy pollution of aquatic microorganisms and organic materials during the period of this study. On the other hand, eight metalic constituents from the water samples were also assayed, and all metalic ions detected were remarkably low below the legal criteria. However, calcium ion in the water samples from the habitats of P. manchouricus was considerably higher than others. Infection rates of digenetic trematodes in the snails were 6.9 percent in P. manchouricus and 4.8 poercent in S. libertina, respectively. P. manchouricus snails harboring with the cercariae of Clonorchis sinensis were only 0.14 percent among the snails examined and other trematode cercariae except cercaria of C. sinensis were; furcocercus cercariae, cercaria of Loxogenes liberum type I and II. S. libertina snails parasitized with the cercariae of Metagonimus yokogawai were 1.5 percent out of the snails examined and no cercaria of Paragonimus westermani was found in S. libertina snails in the present study. Digenetic trematode cercariae other then M. yokogawai in S. libertina snails were: Cercaria yoshidae (B type), Cercaria cristata, Cercaria innominatum, Cercaria of Centrocestus formosanus and Cercaria nipponensis.
parasitology-helminth-trematoda ; Clonorchis sinensis ; Loxogenes liberum ; Metagonimus yokogawai ; Centrocestus formosanus ; Cercaria cristata ; Cercaria innominatum ; Cercaria nipponensis ; epidemiology ; Parafossarulus manchouricus ; Semisulcospira libertina ; Radix auricularia