Studies were conducted in rivers in Kyungpook Province, Korea from July 1970 to September 1974 to determine the stations where Parafossarulus manchouricus, the intermediate snail host of Clonorchis sinensis, are abundant, and the infection rates of these snails with the cercaria of Clonorchis sinensis. Snail collections were made during four consecutive summers(July to September in each year). Ten snail habitats were found. The population density of the snails per square meter of the river bottom ranged from 25 to 250. The highest population of snails was encountered at the Dong-chon station. Cercaria studies by means of the immersing and crushing technics indicated surprisingly low rate of Clonorchis sinensis infection among the snails examined. The proportion of infected snails in Kyungpook Province was 0.8 per thousand of all snails examined. Results indicated that the Parafossarulus manchouricus exists in limited areas within the rivers under study and the infection of the snail with the cercaria of Clonorchis sinensis is very low.
parasitology-helminth-trematoda ; Clonorchis sinensis ; Parafossarulus manchouricus ; snail ; epidemiology

Studies were conducted to determine the ecology of the snail, Parafossarulus manchouricus, the seasonal variation of the snail population, and the infestation rates of these snails with the cercariae of digenetic trematodes, in the snail habitat of river Kumho, in Dongchon of Taegu city, in Kyungpook Province, Korea, from 1975 to 1979. The earliest time the snails were found was early in April every year. At that time the water temperature ranged from 13 to 14 degrees C. The population density of snails ranged from 2 to 8 per square meter. The highest population density of snails was encountered in late June and the water temperature was between 24 and 26 degrees C. The snails disappeared in early and mid-November, when the water temperature dropped to 10-13 degrees C. The average snail population in June was 115.9 per square meter in 1975 but in 1976 dropped abruptly to 30.5 and remained at approximately the same level in 1977. It then decreased at considerably lower rates, with the average of 18.7 in 1978 and 14.5 in 1979. The snails collected in the habitat were examined for the presence of cercariae of digenetic trematodes. Of these, four species, Clonorchis sinensis, Cyathocotyle orientalis, Exorchis oviformis, and Loxogenes liberum were found. The most frequently liberated cercaria was L. liberum 43.3 per cent, followed by E. oviformis 6.2 per cent and C. orientalis 1.5 per cent. The least frequently liberated was C. sinensis 0.1 per cent. In the monthly liberation rates for larval trematodes, the higher rates were observed in June, July and August every year, and the cercarial rates for Clonorchis sinensis, Cyathocotyle orientails and Exorchis oviformis demonstrate a fairly consistently fluctuating downward trend over the five-year period, except for Loxogenes liberum. Summarizing the results, this study indicated that the population density of snails in the habitat and the infection of the snail with the cercariae of digenetic trematodes has decreased over the five-year period from 1975 to 1979.
parasitology-helminth-trematoda ; Clonorchis sinensis ; Parafossarulus manchouricus ; Cyathocotyle orientalis ; Exorchis oviformis ; Loxogenes liberum ; epidemiology ; cercaria

As a part of observation on the suitability as a second intermediate host of Clonorchis sinensis, various infection experiments were tried to Cyprinus carpio nudus. The results obtained were summarized as follows: The cercariae which attempted to contact with Cyprinus carpio nudus in the water were observed under the stereomicroscope. After contact, cercariae began to separate its tails from the bodies at 4 minutes increasingly, and then the number ranged to 80 percent at 13 minutes after the encounter. But very few cercariae could actually invade into the epidermis of the fish. When Cyprinus carpio nudus were exposed to a number of cercariae in the beaker, only a few cercariae could invade through the epidermis. Most of the invaded cercariae were killed before forming the cyst. Also rare encysted cercariae were found to be dead within 48 hours. Cyprinus carpio nudus were reared with Parafossarulus manchouricus shedding numerous cercariae in the indoor aquarium. When observed after 12 days, to determine the susceptibility, no metacercaria was found infected. Cyprinus carpio nudus were reared with Parafossarulus manchouricus shedding numerous cercariae in Kimhae lake for 2 months in summer of 1982, in order to check the natural infection. No metacercaria of Clonorchis sinensis was found from the fish. In the cases of control fish, Pseudorasbora parva, numerous cercariae were inspected on the course of invasion through epidermis of the fish under the stereomicroscope. And many metacercariae were also found from the fish whenever they were kept in beaker, indoor aquarium, or the lake for natural infection. The results suggested that Cyprinus carpio nudus might not be proper intermediate host of Clonorchis sinensis.
parasitology-helminth-trematoda ; Clonorchis sinensis ; Cyprinus carpio nudus ; Parafossarulus manchouricus ; cercaria ; biology

A snail of the primary host of Clonorchis sinensis, distributed in the Korean Penninsula, has been called Bulimus striatulus (Benson) Shiba 1934, while that of China, the mainland of Asia, and of Japan has been called Parafossarulus manchouricus Bourguigant(Abbott l951, Sugihara l954). Having studied on the external character and radula of the snail collected from nine areas of Korea, including Kimhae, Jinyong, Namji, Ulsan, Kunsan etc.The author has not found any reasonable distinctions which set up different species between Korean species and Chinese or Japanese species although there exists some slight difference.
parasitology ; malacology ; helminth ; trematoda ; Clonorchis sinensis ; Bulimus striatulus ; Parafossarulus manchouricus ; Bourguigant

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 epidermal mucous substances of C. carassius which were extracted by ether were separated into various spots on the silica gel thin layer chromatography and separated into various fractions in the silica gel column chromatography, using petroleum ether (30 percent) and chloroform(70 percent) as a solvent. The wormicidal effects of the spots and the fractions on the cercaria, the liberating metacercaria and the adult of C. sinensis, were observed by month giving attention to ambient water temperature. Among the four spots of the thin 1ayer chromatography of the ether extracts from C. carassius, the uppermost first spots (Rf. 0.924-0965) had a strong wormicidal effect on the cercaria in May, June, July, August and September, and the cercaria which came in contact with the materials was killed in 29-49 min., but in other months (Rf. 0.612-0.752) it was killed only after 50-115 min. In column chromatography of ether extracts from C. carassius, the first fractions which had a wormicidal effect killed the metacercariae within 38-163 min. in May, June, July, August, and September, but it took about 120-458 min. to kill them in other months, meanwhile the wormicidal time of the fractions on the adults was 445-835 min. in May, June, July, August and September, but was 878-2,130 min. in other months. The Rf. value of the uppermost first spot of the thin layer chromatography of ether extrart from the mucous substance of C. carassius which was reared in the aquarium controlled at 23 C was 0.79, and its first fraction of column chromatography killed the metacercaria and the adult of C. sinensis within 315, and 1,850 min. respectively. As summarized above, the wormicidal materials of the epidermal mucous substances of C. carassius had no relation to ambient water temperature, but the secretion period of this wormicidal materials was the same as the liberating period of the cercariae from Parafossarulus manchouricus.
parasitology-helminth-trematoda ; Clonorchis sinensis ; Carassius carassius ; Parafossarulus manchouricus ; chromatography ; mucous substance

Clonorchiasis for which no specific therapy is available has been recognized as one of the serious public health problems in terms of waste of human productivity in Korea today and an urgent consideration must be given to its prevention and control. For past several years, the author has been finding that the infection rate of liver fluke in fish from the Kum-Ho river which has long been recognized as the world's notorious prevalent area of the disease, has been decreasing gradually. Here the author formulated the hypothesis that the decreasing of infection rate might be influenced by the common use of pesticide in plants along the river. Basing this hypothesis, the effective use of pesticide may contribute to the control of the disease by cutting the life cycle of liver fluke. To test above hypothesis, molluscicidal effect on Parafossarulus manchouricus and cercariacidal effect of various pesticides in liver fluke have been determined and the following results were obtained. In molluscicidal effect, the most potent agent in low concentration was Bayer 73 which is 3 to 70 times stronger than other pesticides. When compared with NaPCP which has been widely used for the eradication of Onchomelania, Bayer 73 shows 5 to 10 times stronger effect. The order of pesticide in molluscicidal effect was: Bayer 73, Nicotin, NaPCP, Sevin, Parathion, Copper sulfate and Lindane. In cercariacidal effect, the most potent agent was Parathion which had 2 to 5 times stronger effect than Bayer 73 or NaPCP. The order of pesticide in the cercariacidal effect was: Parathion, Bayer73, NaPCP, Lindane, Nicotin,Sevin, and Copper sulfate. By applying the common used concentration of pesticides considering the toxicity to plants, Bayer 73 is most potent in molluscicidal effect and then Nicotin, NaPCP, Copper sulfate, Sevin, Parathion and Lindane in order. In cercariacidal effect, Parathion is the most potent and NaPCP, Bayer 73, Lindane, and Copper sulfate are followed. Considering with the toxicity to human body the most safe and effective pesticides were Bayer 73, Seven, NaPCP, and Copper sulfate but among those agents, Bayer 73 and NaPCP show relatively stronger effect in both Parafossarulus manchouricus and cercaria of liver fluke.
parasitology ; helminth ; trematode ; Clonorhcis sinensis ; chemotherapy ; Parafossarulus manchouricus ; Onchomelania ; cercaria ; toxicology ; Bayer 73 ; Nicotin ; NaPCP ; Sevin ; Parathion ; Copper sulfate ; Lindane

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

In an attempt to clarify the epidemiological feature of C. sinensis in Mangyeong riverside area, the prevalence of clonorchiasis, infestation rate of the cercariae in Parafossarulus manchouricus, and detection rate of the metacercariae in fresh-water fishes were investigated from March 1 to September 30, 1983 at the upper, middle and lower reaches of the river. The results obtained were summarized as follows:Detection rate of C. sinensis egg among inhabitants was 8.2 percent out of a total of 1,266 persons. but the differences in detection rates were not statistically signifcant among upper, middle and 1ower reaches. According to sex, the detection rates were 10.3 percent in male and 6.1 percent in female (p<0.05), but by age groups, increases of the rates were observed as increase in age (p<0.05). Out of a total of 380 fresh-water fishes of 32 different species, 93 fishes (25 percent) of 12 species were found positive with Clonorchis metacercariae, and there were differences in infection rates of the metacercariae among the fishes in 3 parts of the river; 11 percent in upper, 35 percent in middle, and 34 percent in lower reaches respectively. The metacercarial detection rates from various fishes were 97 percent in Pseudorasbora parva, Cultriculus eigenmanni (85 percent), Gnathopogon strigatus (67 percent), Microphysogobio yaluensis (50 percent), Gnathopogon coreanus (47 percent), Pungtungia herzi(44 percent), Abbottina rivularis (40 percent), Moroco oxycephalus (33 percent), Coreoleuciscus splendidus (32 percent), Gnathopogon majimae (26 percent), Rhodeus ocellatus (7 percent), and Aphyocypris chinensis (3 percent) respectively. Although very few P. manchouricus were collected at upper reach, 12 snails (0.7 percent) among a total of 1,713 were found infected with Clonorchis cercariae. Also the cercariae of Echinochasmus japonicus (7.99 percent), Lexogenes liberum (0.99 percent), Cyathocotyle orientalis (0.75 percent), Exorchis oviformis (0.23 percent) and Asymphylodora japonica (0.05 percent) were detected from the snails.
parasitology-helminth-trematoda ; Clonorchis sinensis ; clonorchiasis ; epidemiology ; Pseudorasbora parva ; Cultriculus eigenmanni ; Gnathopogon strigatus ; Microphysogobio yaluensis ; Gnathopogon coreanus ; Pungtungia herzi ; Abbottina rivularis ; Moroco oxycephalus ; Coreoleuciscus splendidus ; Gnathopogon majimae ; Rhodeus ocellatus ; Aphyocypris chinensis ; Parafossarulus manchouricus ; Echinochasmus japonicus ; Lexogenes liberum ; Cyathocotyle orientalis ; Exorchis oviformis ; Asymphylodora japonica