Recently there have been some reports on human infections of Echinostoma hortense in Korea. It was found that a few species of freshwater fishes were playing the role of the second intermediate host of E. hortense. However, molluscan intermediate host has not been identified yet in Korea. The present study aimed to establish the life cycle of E. hortense in laboratory. Experimental studies such as egg production from the rat, development of the eggs in vitro, exposure of miracidia to freshwater snails, shedding pattern of cercariae from infected snails, morphology of cercariae, cercarial infection to the second intermediate host and infection of metacercariae to the difinitive hosts were done. In addition, epidemiological surveys on the infection status in inhabitants and house rats, and on the natural infection of larval echinostomes in the snails and fishes were carried out along the South Hangang-river. The results obtained were as follows: The eggs deposited from adults in physiological saline were cultivated at room temperature (20-24C). The miracidia were firstly observed on 8 days after cultivation, and 85.5 per cent of the eggs contained the mature miracidia on 11 days after cultivation. More than 90 per cent formed the miracidia when cultivated at temperature 22-27C. Hatching of the miracidia began on 12 days after cultivation and continued for a week. The size of the miracidia was 103.0 x 51.4 micrometer in average. The motility of miracidia were active up to 8 hours after shedding, but they were all dead within 10 hours after shedding. A freshwater snail, Radix auricularia coreana was cultivated in aquaria. A hatched F1 snails from the egg masses were exposed to 20 miracidia respectively. Escape of cercariae started on 15 days after infection. Radix auricularia coreana was experimentally identified as the first intermediate host of E. hortense in Korea. Cercarial shedding started on 15-20 days after infection by snail, continued for about 10 days (8.8 days in average). Infected snails were dead within 32 days after the miracidial infection. About 1,335 cercariae (328-1,994) per snail were shed in its life, and 119 cercariae in average per snail per day were shed. The cercariae were motile for more than 24 hours, and then squirming at the bottom until death. The body and tail sizes of cercariae were 356 x 186 micrometer and 510 x 68 micrometer in average, respectively. The rediae parasitized in the snail hosts were found mainly around the pericardial regions, and their size was 1,575 x 258 micrometer in average. The numbers of developing cercariae in a mature redia were 14 in average (7-20 in range). The numbers of rediae in a snail were 102 in average on 15 days after miracidial infection and 221 in average on 28 days. Three uninfected Misgurnus anguillicaudatus, less than 6.5 cm long were used in for the cercaria1 infection. They were all exposed with 755 cercariae, and examined at 5-day intervals starting from 10 days after infection. All the fihes were infected with metacercariae of E. hortense and a total of 275 was found infected (36.4 per cent). The metacercariae were fed to rats and the adult worms were obtained on 15 days after infection. The infected rats began to deposit the eggs on 11 days after infection. The number of eggs deposited per day per worm (EPD/worm) was 400-500 on 3 weeks after infection and was increased to 1,000-1,500 on 4 to 17 weeks, then decreased to 800 on 2l weeks after infection. A total of 745 stool specimens collected from 576 male and 169 female residents of 8 different villages along South Hangang basin was examined. Out of 745 specimens, the eggs of Echinostoma sp. were found in 2 cases (0.3 per cent). Of 34 house rats one showed egg-positive (2.9 per cent). Total 971 Radix auricularia coreana collected from 7 sampling stations were examined for shedding of cercariae. Three snails (0.3 per cent) shed the cercariae of E. hortense. A total of 119 out of 542 freshwater fishes (22.0 per cent) had the metacercariae of E. hortense. The fishes parasitized with the metacercariae were 4 out of 14 examined species. The infection rate of 4 species were 34.1 per cent (106 out of 311) in Misgurnus anguillicaudatus, 30.4 per cent 7 out of 23) in Misgurnus mizolepis, 4.3 per cent (2 out of 46) in Moroco oxycephalus and 22.2 per cent (4 out of 18) in Odontobutis obscura interrupta. In summarizing the above results, the first intermediate host of E. hortense was found as Radix auricularia coreana in Korea. Also it took about 46 days for the shortest completion of a life cycle of E. hortense in summer; that is, 10 days for miracidial development in eggs, 15 days for cercarial development in the snail, about 10 days for metacercarial development in the second intermediate hosts, 11 days for the maturation as the adults in the definitive hosts. The natural infection rates of E. hortense in the intermediate hosts were relatively high but those in the definitive hosts were low in the middle areas of South Hangang basin.
parasitology-helminth-trematoda ; Echinostoma hortense ; epidemiology ; biology ; Misgurnus anguillicaudatus ; Misgurnus mizolepis ; Moroco oxycephalus ; Odontobutis obscura interrupta ; Radix auricularia

The author studied the infection rates of Clonorchiis sinensis in the inhabitants of Kyungpook Province, and surveyed infestation rates of Clonorchis metacercarias in the twelve kinds of fresh water fishes for the purpose of the eradication. plan of clonorchiasis of Kyungpook Province. The examination was continued from April 1960 to October 1962 with 24,252 inhabitants ranging from four months to over sixty aged. All the family were tested intradermally with Clonorchis antigen and then confirmed the eggs by M.G.L. technique. The results of the examination were summarized as follows. I. The infection rate of the inhabitants; In the people tested, 27.7 percent was infected with Clonorchis sinensis. There were no remarkable differences in the infection rates among each Districts; River side inhabitants(Yungchun-Gun 23.6 percent, Andong-Gun 27.4 percent), paddy field inhabitants(Yungchun- Gun 23.6 percent, Sangchu-Gun 29.1 percent) and mountain side inhabitants (Chungsong-Gun 23.8 percent, Yungyang-Gun 27.7%). However, the infection rates of the river side peoples were slightly higher than that of the districts far from the river. The infection rate of the male was 34.98 percent (4 ,628 out of 12,230), while the female was 18.96 percent (2090 out of 11022). The maximum infection rate of the male group was observed in the 35-39 age group (73.8 %) and in female, 55-59 age group (34.l percent) respectively, however it was gradually decreased in the senile group. II. The infection rates of the family group; Those infected in both husband and wife were 28 percent(357 out of 1,289), husband only was 52 percent (672 out of 1,289) and wife only was 4 percent (50 out of 1,289). The children of the infected parents revealed higher morbidity than that of the non-infected parents. The children of the infected father revealed much morbidity than that of the mother's side. On the contrary, children's morbidity rate of the infected widow was higher than that of the widower. III. The infestation rates of fresh water fishes; The metacercaria of Clonorchis sinensis was found in the flesh exclusive of the Misgurnus anguillicaudatus and Zacco platypus in the 11 kinds of fresh water fishes. The maximum infestation rate of 55.8 percent was revealed at Pseudorasbora parva and next to it was Sarcocheilichthys wakiyae of 5l.7 percent. The number of metacercaria in flesh was decreased as compared to the previously examined level.
parasitology-helminth-trematoda-Clonorchis sinensis ; epidemiology ; Misgurnus anguillicaudatus ; Zacco platypus ; Sarcocheilichthys wakiyae ; Pseudorasbora parva

The infection status of the loaches, Misgurnus anguillicaudatus, with the metacercariae of Echinostoma hortense, was studied in Korea. A total of 154 loaches purchased at 4 local makets (Seoul, Kimhae, Naju-gun and Kangjin-gun) were examined their infection rate as well as the density and location of the metacercariae in the fish body. The results are as follews: The loaches carrying the metecercariae of E. hortense were 64 (41.6%) in total number and the metacercarial density ranged 1-29 per infected loach with an average value of 8.1. The highest infection rate and metacercarial density were obtained from the loaches purchased at Kangjin-gun, Jeonranam-do. The metacercaria of E. hortense were chiefly distributed in the distal intestinal wall and the adjacent mesentery, the perianal tissues, and the head and gill of the loaches examined. From the results, it is concluded that the loach is one of the important second intermediate hosts of E. hortense in Korea, and their infection rate and metacercarial density are considerably high.
parasitology-helminth-trematoda ; Echinostoma hortense ; Misgurnus anguillicaudatus ; metacercaria ; epidemiology ; intermediate host

Cercariae of Clonorchis sinensis were attempted to penetrate into various fry of fresh water fishes in order to examine the conditions of infection and the further development in the fish. The following conclusions were made. Cercariae of C. sinensis penetrated into the muscle of the fry of Pseudorasbora parva were found to be able to develop. Cercariae penetrated into the fry of Pseudorasbora parva migrated into the organs of the fry to kill their host. From each dead individual of P. parva, more than 10 larvae of C. sinensis could be discovered. Cercariae attached on the Cyprinus carpio, Carassius and gold fish were almost killed before penetration into the body and even one or two cercariae penetrated were also killed as time passed. Cercariae of C. sinensis infected on the fry of Cyprinus Carpio, Carassius auratus and gold fish could not survive more than 60 days. Cercariae penetrated into Cyprinus carpio and Carassius auratus could not develop into complete metacercariae even after 3O days. Cercariae of Clonorchis sinensis penetrated into the fry of Aplocheilus latipes were killed within 10 hours and the cercariae attached on the caudal fin were destroyed in 2 hours. It was found that no cercariae of Clonorchis sinensis could penetrate into the body of the fry of Misgurnus anguillicaudatus.
parasitology-helminth-trematoda-Clonorchis sinensis ; cercariae ; Pseudorasbora parva ; Cyprinus carpio ; Carassius auratus ; gold fish ; Aplocheilus latipes ; Misgurnus anguillicaudatus ; mucous substance

The author reported in the previous pager on his observation of sudden death of Clonorchis sinensis cercaria before penetration into the body of fry such as Cyprinus carpio and Carassius auratus. And in these studies, the reason behind the fact was investigated and it was found that the mucous substances on the surface of a certain fishes have a strong wormicidal effect to the larva of C. sinensis. When cercariae of C. sinensis were immersed into the mucous substance of gold fish for three minutes 36 seconds to 4 minutes 20 seconds, into that of Aplocheilus latipes for 4 minutes 30 seconds to 5 minutes 20 seconds, into that of Cyprinus carpio for 5 minutes 15 seconds to 6 minutes l6 seconds, and into that of Carassius auratus for 5 minutes 20 seconds to 7 minutes 30 seconds, it was observed that they were all killed. No wormicidal effect against C. sinensis could be observed with the mucous substance obtained from Pseudorasbora parva, Misgurnus anguillicaudatus and Ophicephalus argus. No wormicidal effect against Metagonimus sp. cercaria is observed with the mucous substance obtained from Cyprinus carpio, Carassius auratus. The wormicidal effect of the mucous substances obtained from gold fish was destroyed when heated over 60 C. The movements of metacercaria of C. sinensis stopped after 10 minutes application of the mucous substance obtained from Cyprinus carpio and they were killed within 30 minutes. When the adult worms collected from the bile duct of experimentally infected rabbits for 20 to 60 days, were immersed into mucous substance from Cyprinus carpio, they were killed between 25 minutes and 35 minutes. No wormicidal effect could be observed with the mucous substance obtained from dead Cyprinus carpio, Carassius auratus, gold fish, when applied to the adult worms and larvae of C. sinensis.
parasitology-helmith-trematoda-Clonorchis sinensis, Metagonimus sp. ; Cyprinus carpio ; Carassius auratus ; Aplocheilus latipes ; Pseudorasbora parva ; Misgurnus anguillicaudatus ; Ophicephalus argus ; gold fish ; mucous substance

The present work which was investigated in July 1979, was to observe the wormicidal effects of the external mucous substances of 9 species of fresh water fishes (Cyprinus carpio, Parasilurus asotus, Anguilla japonica, Ophicephalus argus, Carassius carassius; golden crusian carp, Misgurnus anguillicaudatus, Zacco platypus, Pseudorasbora parva and Carassius carassius; crusian carp) on cercaria, liberated metacercaria and adult of Clonorchis sinensis. The mucous substances extracted by ether from the above 9 species of fishes were separated into many spots on the silica gel thin layer chromatography, and divided into many fractions in the silica gel column chromatography which used petroleum ether (30 percent) and chloroform (70 percent) as a solvent. On the silica gel thin layer chromatography of ether extracts from 9 species of fresh water fishes, each of the Rf. values which had wormicidal effect on the cercaria of C. sinensis were different from others; Rf. value of C. carassius (crusian carp) was 0.937, 0.709 in O. argus, 0.612 in A. japonica, 0.576 in P. asotus, 0.451 in C. carpio, 0.701 in Z. platypus, 0.385 in C. carassius(golden crusian carp) and 0.15 in P. parva. Time for wormicide was different from each other, too. It took 14 min. in a case of C. carassius(crusian carp), 25 min. in Z. platypus, 26 min. in C. carassius(golden crusian carp), 28 min. in C. carpio, 30 min. in P. asotus, 35 min. in O. argus, 40 min. P. parva and 180 min. in A. japonica. But any of the spots of M. anguillicaudatus did not show wormicidal effect on the cercaria within 10 hours. In the silica gel column chromatography of ether extracts from 9 species of fresh water fishes, the fractions which had wormicidal effect on the metacercaria of C. sienesis were different from each other; in a case of C. carassius(crusian carp), the first fraction only had wormicidal effect, the 2nd in P. asotus, the 3rd in O. argus, the 4th in C. carassius(golden crusian carp), the 2nd in C. carpio and the 4th in P. parva. Time for wormicide was 40 min. in C. carassius(crusian carp), 52 min. in P. asotus, 74 min. in C. carassius(golden crusian carp), 92 min. in O. argus, 95 min. in C. carpio and 140 min. in P. parva, but any of the fractions of A. japonicas, M. anguillicaudatus and Z. platypus did not show wormicidal effect within 10 hours. The fractions which had wormicidal effect on the metacercaria of C. sinensis had also the same effect on the adult, but it took longer time to kill them. It took 3 hours in a case of C. carassius(crusian carp), 4 hrs. in C. carassius(golden crusian carp), 5 hrs. in P. asotus, 6 hrs. and 6 min. in O. argus, 6 hrs. and 10 min. in C. carpio and half and 6 hrs. in P. parva. But any of the fractions of A. japonica, M. anguillicaudatus and Z. platypus did not show wormicidal effect within 24 hrs.
parasitology-helminth-trematoda ; Clonorchis sinensis ; mucous substance ; Cyprinus carpio ; Parasilurus asotus ; Anguilla japonica ; Ophicephalus argus ; Carassius carassius ; Misgurnus anguillicaudatus ; Zacco platypus ; Pseudorasbora parva

In order to know relationship between the clavate cells of epidermis and infectivity of metacercariae of C. sinensis. histological investigation of epidermis was carried out on the 26 species of fresh-water fish collected from the main rivers in Korea. Results were summarized as it follows: In general clavate cell had a single nucleus at its center. However it was observed in Liobagrus mediadiposalis and Pelteobagrus fuluidraco that clavate cell had two nuclei with and independent so-called light halo of Oxner and in some cases had none of them. In following species; Misgurnus anguillicaudatus, Cobitis taenia, Liobagrus mediadiposalis, Pelteobagrus fuluidraco, Parasilurus asotus and Anguilla japonica, scales were not detected or buried in the dermis layer, and the epidermis was mostly consisted of clavate cells. Among these species, it was observed that no metacercariae were found. In case of Cyprinus carpio, Carassius carassius (crusian carp and golden crusian carp), Sarcocheilichthys czerskii, Pungtungia herzi and Coreoleuciscus splendius, scales were exposed over the epidermis, in which clavate cells were abundantly found. In these species, a few of the metacercariae were detected. On the other hand, no clavate cells were observed in Pseudorasbora parva , Zacco platypus, Microphysogobio koreensis, Gnathopogon majimae, Gnathopogon coreanus, Acheilognathus signifer, Acheilognathus yamatsutae, Cultriculus eigenmanni, Coreoperca herzi, Pseudoperilampus uyekii, Pseudoperilampus notatus and Pseudogobio esocinus. These fishes with exposed scales on the epidermis were well known to serve as the second intermediate hosts of C. sinensis. From the above results obtained, it was suggested that the existance of clavate cells in the epidermis of the fresh-water fish seems to be correlated with the infectivity of the metacercariae of C. sinensis.
parasitology-helminth-trematoda-Clonorchis sinensis ; host ; Liobagrus mediadiposalis ; Pelteobagrus fuluidraco ; Misgurnus anguillicaudatus ; Cobitis taenia ; Liobagrus mediadiposalis ; Pelteobagrus fuluidraco ; Parasilurus asotus ; Anguilla japonica ; Cyprinus carpio ; Carassius carassius ; Sarcocheilichthys czerskii ; Pungtungia herzi ; Coreoleuciscus splendius ; Pseudorasbora parva ; Zacco platypus ; Microphysogobio koreensis ; Gnathopogon majimae ; Gnathopogon coreanus ; Acheilognathus signifer ; Acheilognathus yamatsutae, Cultriculus eigenmanni ; Coreoperca herzi ; Pseudoperilampus uyekii ; Pseudoperilampus notatus ; Pseudogobio esocinu