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

In order to observe the growth and development of Fibricola seoulensis metacercariae, the tadpoles of Rana nigromagulata were experimentally infected with the cercariae. The metacercariae of various developmental stages were recovered from the tadpoles after 2 to 65 days of infection. They were prepared for morphological observation, and were given orally to mice to observe their infectivity. The following results were obtained. All of the tadpoles exposed to the cercariae were observed to harbour the larvae in their abdominal cavity. The young metacercariae of 2 days after infection were 121.1 micrometer long and 63.3 micrometer wide. They grow linearly for the first 14 days to be 262.0 micrometer long and 166.4 micrometer wide. Thereafter, no more growth recognized until 65 days. The larvae of 2 days old were similar with cercarial body and had 2 suckers, a pharynx, two ceca and a primordium of germ cells but no tribocytic organ. On the 8th day, they had tribocytic organ, and their morphology resembled that of mature metacercariae. The metacercariae younger than 10 days could not infect the mice. Only the metacercariae older than 14 days had infectivity. The recovery rate increased by the age of metacercariae from 19.0% in 14 days old to 70.0% in 40 days old. Above findings indicate that the tadpole is indispensible for metacercarial development and it needs at least 2 weeks for maturation. The tadpole is a pivotal host in the life cycle of F. seoulensis for connection between the snail and the frog.
parasitology-helminth-trematoda ; Fibricola seoulensis ; metacercaria ; development

The distribution and the infestation rates of metacercariae in fishes from the Kum-Ho river were observed from June 1965 to August l967. The results obtained are as follows: The Fourteen kinds of metacercariae; Exorchis oviformis, Metorchis orientalis, Cyathocotyle species, Metacercaria hasegawai, Clonorchis sinensis, Metagonimus species, Pseudexorchis major, Echinochasmus species, Centrocestus species, Prosorhpynchus species, and four kinds of unidentified species, A, B, C and D were detected from 12 kinds of fishes. Clonorchis sinensis, Metagonimus species, Echinochasmus species, and Centrocestus species of the detected 14 kinds of flukes were noted to be parasited in man; Metorchis orientalis and Cyathocotyle species in avian species; and Exorchis ovifomis and Pseudexorchis major in wels, but the definite host of the other 6 kinds of flukes were not identified. Exorchis oviformis was found in 64.5 percent, of all kinds of fishes, Cyathocotyle species in 36.8 percent of 7 kinds of fishes, Metacercaria hasegawai in 36.3 percent of 8 kinds, Clonorchis sinensis in 95.0 percent of 6 kinds and Metagonimus species in 47.9 percent of 10 kinds. Concerning the infested rates of metacercaria and the length of fishes, Exorchis oviformis and Clonorchis sinensis showed increased rate by the length of fishes but the rest of fishes showed no relationship between them. The infested degree of metacercaria of Clonorchis sinensis was highest in Pseudorasbora parva with 34.3 parasites per cubic cm of flesh, of Exorchis oviformis in Carassius carassius with 7.3, of Cyathocotyle species in Acheilognathus with 6.0, and of Metacercaria hasegawai in Pseudogobio esocinus with 5.7 but Prosorhpynchus etc. were very few in all kinds of fishes. The infested rates of metacercaria in the four kinds of fishes, Pseudorasbora parva, Pungtungia herzi, Pseudogobio esocinus and Gnathopogon coreanus seemed not to be influenced by season, Spring and Autumn. In the infested rates of metacercariae by parts of fishes, Exorchis oviformis was chiefly infested in scales and fins; Metorchis orientalis, Cyathocotyle species, Clonorchis sinensis, Pseudexorchis major, Centrocestus species and Prosorhpynchus ecinatus were chiefly infested in muscle; Metacercaria hasegawai in muscle and fins; Metagonimus species chiefly in scales; and Echinochasmus chiefly in gills.
parasitology-helminth-trematoda- Exorchis oviformis-Metorchis orientalis-Cyathocotyle species-Metacercaria hasegawai-Clonorchis ; epidemiology ; metacercaria

A group of metacercariae encysted in the flesh of Mugil sp. were identified to be Stellantchasmus falcatus by the morphology of adult worms obtained experimentally. It is confirmed that mullets serve as a second intermediate host of this heterophyid fluke in Korea.
parasitology-helminth-trematoda ; Stellantchamus falcatus ; metacercaria ; Mugil sp. ; intermediate host

The author investigated the larvicidal action of liquid nitrogen against the metacercariae of Clonorchis sinensis, with an observation on the freshness and change of taste in the flesh of fishes. The results obtained were as follows: The metacercariae in the flesh of Pseudorasbora parva, which were treated with liquid nitrogen (-192C), were not killed within 10 seconds, but completely killed over 30 seconds. In comparison, the metacercariae in the flesh of P. parva kept in a refrigerator (-12C) were killed only in 84 percent in 10-hour exposure group. The freezing speed of fishes by liquid nitrogen was 4 min. (') and 15 seconds(") for Cyprinus carpio, 1'22'' for Carassius carassius and only 30'', for Pseudorasbora parva. As for the freshness and taste of raw fresh water fishes, they were not deteriorated after the treatment with liquid nitrogen. In animal infection experiment of C. sinensis metacercariae after freezing, they were found not infective after they were treated with liquid nitrogen. From the results, it is inferred that the treatment of fresh water fishes for longer than 30 seconds with liquid nitrogen is helpful to reduce the possibility of C. sinensis infection without alteration of the freshness and taste of fishes.
parasitolgy-helminth-trematoda ; Clonorchis sinensis ; metacercaria ; toxicology ; liquid nitrogen

The Hongcheon river system flows down through the Hongcheon area of Kangwon-do, and reaches to the Cheongpyeong Dam in Kyonggi-do. Stool specimens from the inhabitants residing along the Hongcheon river basin were examined to detect infection rate of Metagonimus sp., and the intermediate hosts were collected to detect larval stages. The results obtained were as follows: Thirty-nine (33 males and 6 females) out of 529 (314 males and 215 females) inhabitants were infected with Metagonimus sp., showing a total positive rate of 7.4 per cent. In eight areas surveyed, the specimens from Kulji-ri of Bukbang-myon at the middle part of the river showed the highest positive rate of 26.9 per cent (14 positives out of 52) (males; 38.2per cent). The specimens from Mogog-ri of Seo-myon at the downstream of the river showed a positive rate of 10.4 per cent (13 positives out of 125) (males;12.6 per cent). The positive rates in other regions were less than 10 per cent. The density of the first intermediate host, Semisulcospira sp., was the highest in Kulji-ri of Bukbang-myon (10-20 snails per m(2)), and the infection rate of Metagonimus cercariae in the snails was 10.7 per cent(13 positives out of 121 snails). The infection rate of Metagonimus metacercariae in Zacco platypus, the fresh water fish favorably eaten raw by the inhabitants, was 68.2 per cent (30 positives out of 44 fishes), and most metacercariae were detected under the scales (89.9 per cent). Adult flukes were obtained from the small intestine of a rat, 15 days after infection with the metacercariae obtained from Z. platypus. These adult flukes were identified to be the same srecies as those obtained from human hosts. By this survey, new endemic areas of Metagonimus infection were discovered along the Hongcheon river basin and the main source of infection was the fresh water fish, Z. platypus.
parasitology-helminth-termatoda ; Metagonimus sp. ; epidemiology ; metacercaria ; Zacco platypus

The fresh water snail, Hippeutis(Helicorbis) cantori, caught from the rice paddies in Namyangju-gun, Gyeonggi-do, was found to be a new second intermediate host of E. cinetorchis in Korea. The metacercariae were found from 89(76.7 %) out of 116 snails examined and the average metacercarial burden was 4.7 per infected snails. Some developmental characteristics of E. cinetorchis were observed after experimental infection of the metacercariae to rats and mice.
parasitology-helminth-termatoda ; Echinostoma cinetorchis ; Hippeutis cantori ; metacercaria ; epidemiology ; development

An epidemiologic survey along the several sites of southern coastal areas of Korean peninsula was performed to know the infection status of Parvatrema spp. metacercariae in Tapes philippinarum. The clams were purchased from 13 coastal areas in Kyongsangnam-do and Chollanam-do, in September, 1990. Each of them was digested with pepsin-HCl solution and examined under a stereomicroscope for the recovery of metacercariae. A total of 232 (77.3%) out of 300 examined clams were proved to have 1 to 273 Parvatrema spp. metacercariae (54.7 in average). None of the clams from Samsan-myon Kosong-gun and Dolsan-up, Yochon-gun was infected with metacercariae. However, all of the clams from Yonghyun-myon, Sachon-gun, Dohwa-myon, Kohung-gun, Ahllyang-myon, Changhung-gun and Chiryang-myon, Kangjin-gun was infected with about 71, 31, 80 and 42 metacercariae respectively. Of the clams from Kohyun-myon, Namhae-gun, Doam-myon, Kangjin-gun and Kusan-myon, Uichang-gun examined, 97.5%, 95.0% and 90.0% were infected with about 117, 76 and 28 metacercariae. In other 4 surveyed areas, Seolchon-myon, Namhae-gun, Hwayang-myon, Yochon-gun, Byollyang-myon, Sungju-gun and Bukpyung-myon, Haenam-gun, 55.0%-80.0% of clams were positive, and their average intensity of infection ranged from 6 to 25 metacercariae. From these results, it was confirmed that Tapes philippinarum from southern coastal areas of Korea are highly infected with Parvatrema spp. metacercariae.
parasitology-helminth-trematoda ; Parvatrema ; metacercaria ; epidemiology ; Tapes philippinarum

The metacercariae of Echinostoma cinetorchis (Trematoda: Echinostomatidae) were found infected in the loaches (Misgurnus anguillicaudatus) purchased from two local markets in Korea. Identification of the metacercariae was done after obtaining adult worms from experimentally infected albino rats. Brief course of worm development in rats was also observed up to 28th post-infection day. The results are as follows: The metacercariae of E. cinetorchis were detected from 5 (10.9 percent) out of 46 loaches examined and the average metacercarial burden per infected loach was 34.4. They were always found from the posterior abdominal wall. The worm recovery rate from 8 rats was 24.6 percent in average. It was observed that the rate decreased according to age of infection; from 40.7 percent after 6 days to 15.0 percent after 28 days. The adult worms were morphologically characterized by the presence of head crown with dorsally uninterrupted collar spines, 37-38 in number, and the tendency of migration or disappearance of testes. So that they were identified as Echinostoma cinetorchis Ando et Ozaki, 1923. The development of worm was very rapid during 6-10 days after infection and became much slower thereafter. During the rapid worm growth the development of genital organs was more prominent than that of non-genital organs. From the results it is concluded that the loach is involved in the life cycle of E. cinetorchis in this country and may take a role for infection source to animals and man. It is also confirmed that migration or loss of testes is the distinct specific character of this echinostomatid fluke.
parasitology-helminth-trematoda ; Echinostoma cinetorchis ; metacercaria ; mouse ; development

This study was carried out to outline the geographical distribution of the sweetfish which were infected by the metacercariae of Metagonimus yokogawai from August to October in 1979. The infection status was examined both by the muscle compression method and by digestion technique. The result was summarized as follows: A total of 197 sweetfish, Plecoglossus altivelis was collected, 125 fish from 5 streams along the East Coast and 72 fish from 4 streams along the South Coast. Total 125(63.5 percent) fish were infected by the metacercariae of M. yokogawai. The rate and intensity of infection in the south coastal areas were much higher than those in the east coastal areas; the rate was 42.4 percent in the East and 100 percent in the South, mean number of metacercariae per fish was 721 in the East and 14,308 in the South, and mean number of metacercariae per gram of flesh was 43 in the East compare with 904 in the South. The sweetfish infected by the metacercaria of M. yokogawai were newly observed in 5 foci, i.e., Yeongogcheon in Myeongju Gun and Namdaecheon in Gangneung Si, Gangweon Do and Wangpicheon in Uljin Gun, Gyeongsangbug Do in the East, and a branch of Namgang in Euiryeong Gun and Sinhyeoncheon in Geoje Gun, Gyeongsangnam Do in the South. The rate of metacercarial infection was 4.1 percent in Yeongogcheon and 100 percent in others. The number of metacercariae in a fish ranged from 9 to 45,018 and the number of metacercariae per gram of flesh was the lowest in Gangneung Namdaecheon as 19 and the highest in Geoje Sinhyeoncheon as 1,237. Summarizing these findings with previous records, M. yokogawai might be prevalent in the streams along the East Coast southern from Myeongju Gun, Gangweon Do and along the South Coast in Korea.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; sweetfish-Plecoglossus altivelis-epidemiology ; metacercaria