Metacercariae were found from 6 samples among 4,382 Parlemon nipponensis which were caught at Podu, Kohung, Korea. The metacercaria was inclined as a larval stage of Paragonimus westermani by following reason: Semisulcospira libertina was the only one species which lives in Podu area. No other metacercaria except Paragonimus westermani were found from the craw or cray fish which were caught in the endemic aera. Metacercariae, ovary, testes and cuticular spines resmbled the characteristics of Paragonimus westermani, which have been described by previous workers.
parasitology ; helminth ; trematoda ; Paragonimus westermani ; metacercaria ; epidemiology

This survey was undertaken to determine the recent prevalence of lung fluke, Paragonimus westermani, in the three localities of Wiseong county, Kyungpook Province, Korea and to compare the prevalence among the residents in the same areas between 1924 and 1980. The three localities, Ku-seong, Sam-chun, and Um-ji villages (dong) have been known as the endemic areas of Paragonimus westermani. The surveys were made on the general population. They were examined using intradermal test with Paragonimus westermani antigen, and the diagnosis of paragonimiasis was made depending on the positive intradermal reaction. The sputum examination could not be performed beacause the residents were inaccessible. The prevalence of Paragonimus westermani among the residents in the three communities varied from 1.4 percent to 7.9 per cent, with an average of 4.0 per cent. Whereas, the average reported by Ichinomiya in 1924 was 4.7 percent. There are no significant differences in the sex and age specific rates of infection between 1924 and 1980. With the abundant density of Semisulcospira snails and crayfish in Sam-chun stream and the high rate of infection with Paragonimus westermani among the residents in the village, it is found that Sam-chun village, one of the three localitied in Wiseong county, where Ichinomiya (1924) surveyed, was still the endemic focus of Paragonimus westermani.
parasitology-helminth-trematoda ; Paragonimus westermani ; paragonimiasis ; epidemiology

In order to determine the epidemiological patten of the liver fluke, Clonorchis sinensis, the locality where the snail, Parafossarulus manchouricus, is abundant, the infestation rates for the cercarial and metacercarial larvae of digenetic trematodes in the snail and fish hosts, and the prevalence of Clonorchis sinensis among the residents in the vicinity of river Taewha, Kyungnam Province, Korea were studied from March 1979 to September 1980. Four snail habitats were found in the river Taewha. The population density of the snail per square meter of the habits ranged from 10 to 500, with an average of 150. Among the 4 snail habitats, three, Baek-cheon, Sa-yeon and Taewha had snails infected with the cercaria of Clonorchis sinensis, and the proportion of infested snails in the three habitats was very low, the average being 0.59 per thousand. Four species of fresh-water fish, the bullhead, Coreobagrus brevicorpus, the Korean shiner, Gnathopogon atromaculatus, the flat bitterling, Paracheilognathus rhombea, and the striped shiner, Pungtungia herzi among ten species of fish examined harbored the metacercaria of Clonorchis sinensis. The intensity of infestation with the cyst of Clonorchis sinensis in the four species of fish was low. The approximate number of the cysts per gram of flesh was between 3.5 in Paracheilognathus rhombea and 21.5 in Gnathopogon atromaculatus. Seven kinds of laval tremathodes, Clonorchis sinensis, Cyathocotyle orientalis, Echinochasmus species, Exorchis oviformis, Metacercaria hasegawai, Metagonimus yokogawai and Metorchis orientalis were found from ten species of fish examined. In general, the infestation rates for the encysted larvae of digenetic trematodes varied from fish to fish. The infection rate for Clonorchis sinensis among the residents in the vicinity of river Taewha was relatively high, 22.2 percent by the formalin-ether sedimentation technique, and the difference in the rate of infection between males and females found to be siginificant(t>2). Of these, the rate was 12.4 per cent in 483 elementary school children and 17.7 percent in 761 middle and high school students. The results obtained in the present study indicate that endemic foci of Clonorchis sinensis exist in the river Taewha and the prevalence of the liver fluke among the residents is still high.
parasitology-helminth-trematoda ; Clonorchis sinensis ; epidemiology

Prevalence study of Metagonimus yokogawai infection, survey of intermediate hosts of Metagonimus yokogawai and food habits of raw sweetfish among inhabitants along Boseong river (120 km), Jeonra Nam Do (province) were carried out. The results are summarized as follows: Among 360 examined, the egg positive case were 128(35.6 percent); male 112(46.7 percent), female 16(13.3 percent). The prevalence rates were different by geographical areas; 42.4 percent in down stream, 49.4 percent in middle stream and 13.3 percent in upper stream. By ages, highest rate, 53.6-59.1 percent was observed among 30-49 group (male 69.6-73.0 percent, female 15.8-35.5 percent). Eggs per gram of feces were 2,084 (200-12,280) in average; down stream 1,708, middle stream 2,590, upper stream l,550. By social strata, the prevalence showed differences; 24.8 percent in primary schoolchildren, 78.4 percent in school teacher and local officers, 30.6 percent in general inhabitants. Clonorchis sinensis infected cases in the areas were 21(5.8 percent) out of 360 examined, and 90.5 percent of them showed mixed infection with Metagonimus yokogawai. Cercariae of Metagonimus yokogawai from the lst intermediate host, Semisulcospira sp., in down and middle streams were detected from 32 snails (5.9 percent) out of 545 examined. All the 22 Plecoglossus altivelis which were caught from the down stream were infected with metacercariae of Metagonimus yokogawai. The number of the metacercariae detected was 22,650 per fish in average, and the number increased from August to October. Experiences of raw sweetfish intake of the inhabitants were found in 208(58.4%) among 356 interviewed by questionaire form (male 76.7 percent, female 20.7 percent). Means of acquisition of the sweetfish were mostly by purchase 68.8 percent, and seasonally in summer. Reason of the raw sweetfish intake was due to the flavor, 83.2 percent. The fish were mixed in soy sause with vinegar before the intake.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; metagonimiasis ; epidemiology

The present survey was undertaken to observe the geographical distribution of metacercaria among the sweetfish, Plecoglossus altivelis, the most important second intermediate host of Metagonimus yokogawai, which were collected during the period from 1983 to 1984 in south-eastern coastal areas of Korea. The results obtained were summarized as follows: A total of 668 sweetfish collected from 70 chons (=streams) in the above coasta1 areas was examined for the metacercariae, and 432(64.7 percent) among them were infected with metacercariae of M. yokogawai. The mean number of metacercariae in a fish was in the range from 0 to 29,604 and the mean number of the metacercariae in a fish was 640.3. It was observed that the mean infection rate showed 46.4 percent in Gangweon-Do (=province). The infection rates varied from stream to stream showing 100 percent in Namdae stream(Gangnun-city), Obsib-stream(Samchok-gun) and Dongmak, 95.0 percent in Hosan stream, 90.0 percent in Gungchon stream, and Namdae stream (Yangyang-up), 80.0 percent in Hwasang stream, 50.0 percent in Daebong stream, 45.0 percent in Yonghwa stream, 30.0 percent in Sangchon stream and Sachon stream, 20.0 percent in Munam stream and Okgyoe stream, 15.0 percent in Imweon stream, 10.0 percent in Namchon stream. And no metacercarial infections in their fish host were found in the areas of Mulchi stream, Sangun stream, Gosamun stream, Jonchon stream snd Gagok stream. It was observed that the mean infection rate showed 50.9 percent in Kyongsangbuk-Do(=province). The infection rates also varied from stream to stream showing 100 percent in Songchon stream, Osib stream (Yongdok-gun) and Daejong stream, 60.0 percent in Pyonghae stream snd Gunmu stream, 50.0 percent in Buhwung stream, 25.0 percent in Nagok stream, 20.0 percent in Oangbi stream, 10.0 percent in Namhodong stream. And no metacercarial infections in their fish host were found in the areas of Namdae stream (Uljinup) and Choksan stream. It was observed that the mean infection rate showed 67.6 percent in Kyongsangnam-Do(=province). The infection rates varied from stream to stream showing 100 percent in Taehwa river, Hwiya river, Inchon stream, Miryang river, Nam river, Hwagae stream, Koha stream, Sosang stream, and Tongchon stream, 90.9 percent in Yoncho stream, 90.0 percent in Hoihwa stream, 80.0 percent in Chindong stream, 66.7 percent in Chingyo stream, 40.0 percent in Hoyam river. And no metacercarial infections in their fish host were found in the areas of Chinjon stream, Sanchon stream and Jukchon stream. It was observed that the mean infection rate showed 94.6 percent in Chollanam-Do(=province). The infection rates varied from stream to stream showing 100 percent in Dongchon stream, Isachon stream, Somjin river (Goksong-gun), Somjin river (Kurye-gun), Sosi stream, Gokchon stream, Kohung stream, Kwansan stream, Youi stream, Unjon stream and Apnae stream, 92.3 percent in Tamjin river, 90.9 percent in Okkok stream, 84.6 percent in Songgun stream. And no metacercarial infections in their fish host were found in the area of Yongok stream. On the other hand, the infection rate showed 100 percent in Inchon river of Chollabuk-Do (=province) and Kangon stream of Cheju-Do (=province).
parasitology-helminth-trematoda ; Metagonimus yokogawai ; epidemiology ; Plecoglossus altivelis

The Parasitological investigation on the encysted metacercariae in brackish water fish, Tribolodon taczanowskii, in the downstream of Hyungsan river which is located in Kyungpook Province of Korea, were carried out serially and the following results were obtained. Metacercariae of Pseudexorchis major were found in six fishes(15.8 per cent ) out of 38 examined. Parasitic frequencies of the encysted metacercaria of Psedexorchis major in Tribolodon taczanowskii were 15.8 per cent (6 out of 38) in the scale, 10.5 per cent (4 out of 38) in the fin, 13.2 per cent (5 out of 38) in the gill, 10.5 per cent (4 out of 38) in the oral cavity and 7.9 per cent (3 out of 38) in the flesh. The worms were identified as Pseudexorchis major (Hasegawa, 1935) Yamaguti, 1938 by morphological studies on the metacercariae, excysted metacercariae, adults and eggs, and compared with prereported Pseudexorchis species.
parasitology-helminth-trematoda ; Pseudexochis major ; Tribolodon taczanowskii ; epidemiology

Among 11,005 inhabitants(61% of total population) surveyed in 13 villages of Che Ju Island in 1964, were identified as paragonimiasis patients, of these 1,355 were treated with 40 mg/kg body weight of bithionol for 10-15 doses. The purpose of the study was to test whether mass chemotherapy of the human host may provie an answer for the control of paragonimiasis in an area where the human host is main source of infection to the intermediate hosts. The efficacy of the mass chemotherapy as control program was measured by the acceptance of the survey and treatment by the inhabitants, the efficacy and the toxicity of the drug applied, and the influence of the infection rates of the intermediate hosts. The acceptance of the survey and the treatment was not entirely satisfactory: an estimate based on data suggests that only fifty to sixty percent of all cases infected were detected, and 93% of detected cases were treated in the primary program. All cases detected during the follow up survey, which could not cover whole population, were treated. The efficacy of bithionol was excellent when the treatment was completed. 40 mg/kg body weight for 10-15 doses was sufficient to turn the sputum egg-negative except in a few cases infected heavily that needed 20 doses. Side reactions were generally mild; the most frequent reaction was gastrointestinal; which spontaneously subsided within a few to several days. The infection rate of intermediate hosts started to decrease from the third year of the mass treatment with a pattern of gradual drop. Follow up studies on general population in three and four years of the mass treatment also showed markedly decreased prevalence of paragonimiasis by intradermal test and sputum examination. It is concluded that a complete mass chemotherapy with bithionol in an area where human is the main source of infection to the intermediate hosts can be the answer for control of paragonimiasis.
parasitology-helminth-trematoda ; Paragonimus westermani ; epidemiology ; chemotherapy ; bithionol

In this study the authors observed the status of water contamination by crayfish, Cambaroides similis, either alive or dead infected with Paragonimus westermani. The crayfish used as materials were infected heavily with metacercariae of Paragonimus westermani. The live crayfish were kept in water for a long time, and then the sediments of the water were examined to find out whether or not the liberation of the metacercariae from the body of the crayfish had caused contamination of the water with metacercariae. Killed crayfish were also preserved in water for some time. Physical stimuli in terms of mederate degree of shaking were added to the preserved water once a day and half amount of the water was replaced with tapped water of same temperature everyday. Status of the decay of the crayfish, liberation of the metacercariae from the body of the crayfish or contamination of the preserved water by the metacercariae, and numbers of metacercariae harboured in the body of the crayfish were examined everyday. The fate of the metacercariae liberated from the crayfish into water was also observed. Status of the decay of the crayfish, liberation of the metacercariae from the body of the crayfish or contamination of the preserved water by the metacercariae, and numbers of metacercariae harboured in the body of the crayfish were examined everyday. The fate of the metacercariae liberated from the crayfish into water was also observed. The results of this study can be outlined as follows: No metacercaria was detected in the water which contained live crayfish infected with Paragonimus westermani. The preserved water with dead or killed crayfish was found to be contaminated by the metacercariae of Paragonimus westemani, which had been caused by the decay and dispersion of the flesh of the crayfish The liberated metacercariae survived for 10 days in the water at 21-27 C. The liberated metacercariae were found to be sinking into water of s.g. 1.000 with average velocity of 35.8 cm per minute.
parasitology-helminth-trematoda ; Paragonimus westermani ; epidemiology ; crayfish ; Cambaroides similis

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: 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. 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. 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.
parasitology-helminth-trematoda ; clonorchiasis ; metagonimiasis ; Clonorchisis sinensis ; Metagonimus yokogawai ; epidemiology

An epidemiological survey on Metagonimus yokogawai infection was performed in the eastern coast area of Kangwon province. Formalin-ether concentration technique and Stoll's dilution egg counting method were employed to figure out the prevalence and intensity of M. yokogawai infection and eating habits of inhabitants with raw freshwater fish. The results are summarized as follows: The prevalence rate of M. yokogawai infection was 6.6% among a total of 2,357 examinees; 8.6% (115 out of 1,345) in male and 4.0% (40 out of 1,012) in female. The prevalence rates were different by the streams where the examinees were residing: 17.8% along the area of Ohsip-cheon (stream), 11.8% along Maeup-cheon, 1.7% along Hwasang-cheon, 1.3% along Yeongok-cheon, 0.9% along Namdae-cheon, 0.9% along Sa-cheon and 0% in the other streams (Yongchon-cheon, Kangnung Namdae-cheon and Jusoo-cheon) in decreasing order. By social strata, the positive rate was 8.0% (122 out of 1,521) in general inhabitants and 3.9% (33 out of 836) in school children. By the intensity of infection by means of EPG counts in feces; the light infection (less than 400/EPG) was 74.1%, moderate infection (401-1,000/EPG) 17.3% and heavy infection (more than 1,001/EPG) 8.6%. Twelves out of 50 sweetfish (Plecoglossus altivelis) (24%) caught from the streams in eastern coast of Kangwon-Do were infected with metacercariae of M. yokogawai, and the number of larvae detected were 70.7 per fish in average. The metacercarial infection rate in fish were also different by the streams; 100% in Ohsip-cheon of Samcheok-Gun, 14.3% in Sa-cheon, 16.7% in Yeongok-cheon of Myeongju-Gun and 0% in Namdae-cheon of Yangyang-Gun, respectively. Six hundred ninety five (695) out of 1,396 inhabitants and school children (49.8%) were experienced in eating raw freshwater fishes (Plecoglossus altivelis, Tribolodon hakonensis, Coreoperca sp., Moroco sp., Carassius sp. & Cyprinus sp. and Zacco platypus). The data were assayed with the questionnaire collected from the examinees. In summarizing the above results, it is known that the Ohsip-cheon area of Samcheok-Gun is highly infected region, and the other areas of Kangnung Namdae-cheon, Yeongok-cheon and Yangyang Namdae-cheon are very lowly infected or non-infected regions for M. yokogawai infection.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; epidemiology ; Plecoglossus altivelis