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

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 life cycle of Fibricola seoulensis was studied in the laboratory and in the field, with special interests in the larval developments within the eggs and in the intermediate hosts. The first emergence of miracidia after incubation of eggs in 26C water began on the ninth day. The miracidia, elongate and cylindrical shape, had epidermal plates in the formula of 6, 9, 4 and 3, with two pairs of flame cells and lateral processes. A kind of fresh water snail, Hippeutis (H.) cantori, was found to shed furcocercous cercariae from the 13th day after experimental challenge with miracidia while Physa acuta failed to shed. The same kind of snail collected from the field also shed the same cercariae. The cercariae were equipped with 2 pairs of penetration glands and 5 pairs of flame cells. The tadpoles of Rana nigromaculata were found susceptible to experimental infection with the cercariae. The same kind of tadpoles collected from various areas were also found naturally infected. The metacercariae in the tadpoles which were infected experimentally became infective to the definitive host in 21 days. The metacercariae were located free in the body cavity of tadpoles, and attained sexual maturity in rats in 7 days. The present study successfully followed the complete life cycle of F. seoulenis and found that it is possible to maintain the life cycle in the laboratory.
parasitology-helminth-termatoda ; Fibricola seoulensis ; biology ; rat ; Hippeutis cantori ; Rana nigromaculata ; Physa acuta ; intermediate host

Two cases of human Echinostoma hortense infection and their probable infection source were identified by praziqantel (Distocide) treatment of the patients and by examining two kinds of fresh water fish which were eaten raw by them. The result of the research can be summarized as follows: The patients, each aged 31 and 30, were residing in the same house in Wonju City, Kangwon Province. The first case was hospitalized due to epidemic hemorrhagic fever (E.H. fever) and the second case was healthy but had slight degree of abdominal pain and diarrhea from time to time. In the stool examination, eggs of E. hortense (114.3 x 71.0 micrometer average from the first case and 119.1 x 68.3 micrometer average from the second) were found. By administering single dose of praziquantel (10~15 mg/kg) and purgation with magnesium salt to them, six adults of E. hortense were collected from the diarrheal stools of the second case. By examining 84 Moroco oxycephalus and 20 Carassius carassius which were captured at the place where the two patients had captured and eaten the fresh water fish, the metacercariae of Echinostoma sp. were found from 3 (3.5 percent) M. oxycephalus. After the experimental infection of 3 isolated metacercariae to one albino rat three adults of E. hortense were recovered. By the present study, the two patients revealing the echinostomatid eggs in their stools were proven to be infected with E. hortense and to be the second and third human cases of this fluke infection in Korea. Moroco oxycephalus harboured the metacercariae of E. hortense and appeared to be a new second intermediate host.
parasitology-helminth-trematoda ; Echinostoma hortense ; case report ; intermediate host ; rat ; Moroco oxycephalus ; Carassius carassius

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

In order to determine the epidemiological pattern of the Paragonimus westermani, the infestation rates of the cercarial and metacercarial larvae of digenetic trematodes in the snail and crayfish host, and the prevalence of Paragonimus westermani among the residents in the vicinity of the stream Namdae, Wyangpi, and Kwang, in the Ulchin county, Kyungpook province were studied from March to October in 1984. The population density of the snails per square meter of the habitats ranged form 5 to 25, with average of 15. Among the seven habitats, one, Ducheon, had snails infested with the cercariae of Paragonimus westermani, and the proportion of infested snails was very low, the average being 0.152 per thousand. Of six hundred and four crayfish examined, 113 or 18.7 per cent harboured the encysted larvae of Paragonimus westermani. A high infestation rate for the metacercariae in the crayfish was found in two habitats; 39.0 per cent in the Ducheon and 21.6 per cent in the Sokwang. The prevalence of Paragonimus westermani among the residents in Ulchin county was relatively high, 25.8 per cent by the Paragonimus intradermal tests and the difference in the rate of infection between males and females was found to be significant(t>2). The results obtained in this study indicate that endemic foci of Paragonimus westermani exist in Ulchin county and the prevalence of this lung fluke among the residents is relatviely high.
parasitology-helminth-trematoda ; Paragonimus westermani ; paragonimiasis ; epidemiology ; intermediate host ; crayfish ; snail ; metacercaria

The seasonal variations of the rate and intensity of metacercarial infection of C. sinensis in P. parva were observed. The fish were collected at Sun-Am river which located in Kim-Hae City, Kyong-Sang-Nam Do(=Province), Korea, from March 1983 to February 1984 every month. A total of 788 fish was examined. The number of metacercariae in each fish was individually counted after the individual digestion by artificial gastric juice. The result was as follows: During one year, 513(65.1%) out of 788 fish were infected with metacercariae. In May, June, July and September, the infection rates ranged from 82. 0 % to 98. 6% whereas the rates was relatively low in March, April, November and February raning from 11. 4% to 64.7%. The intensity of infection was similar with those of infection rates. The mean intensity per infected fish was 103.0 and standard deviation was 118.9 throughout one year. The highest mean intenstiy was in June(294. 8) and the lowest in Novebmver(11.1). The observed frequency of fish with certain intensities of metcercariae were fitted to theoretical equations derived from negative binomial distribution in March, April, November and February(p>0.05). Meanwhile, the equation of lognormal distribution were fitted with the observed frequencies in May, June, July and September(p>0.05, p>0.75). The variance/mean ratio varied by month. The value was the highest in July(814.3) and the lowest in November(158.8). Unlike our hypothesis, the metacercarial density of Clonorchis sinensis in its the most favourable fish host, Pseudorasbora parva showed considerable seasonal variations in the hyperendemic area. The possible factors were discussed.
parasitology-helminth-trematoda ; Clonorchis sinensis ; epidemiology ; Pseudorasbora parva ; metacercaria ; negative binomial distribution ; intermediate host ; lognormal distribution

In order to judge appropriately the suitability as the second intermediate host of Clonorchis sinensis, the present experiments were proposed to survey the metacercaria of C. sinensis in the fish host, Cultriculus eigenmanni, in the field, and to observe, by experimental infection of the fish with Clonorchis cercaria, the penetrating ability of the cercaria, maturity, the process of degeneration and extinction, and infectivity of the metacercaria. The following is a brief summary of the leading facts gained through the experiments. All the ten fish (mean body weight 13.4 +/- 3.43 g) which were caught in Ok-ku irrigation reservoir were infected with the metacercariae and the average number of the metacercariae found in the fish body/gram was 4.55. The fish was easily subject to invasion of the cercaria, and the examination of the cercariae after having the fish infected disclosed that 24 hours after the infection, all of the cercariae formed their cysts in muscle and the metacercariae kept growing, that 7 days later the metacercariae were found folding their bodies twice, and that in 15 days the characteristic structure of the metacercariae was complete and made a vigorous rotary movement intermittently. In the case of control fish, Pseudorasbora parva, both penetrating ability of the cercariae and the infective degree of the metacercariae to control host were stronger as compared with the fish host because that the control fish had higher suceptibility to C. sinensis. Afterwards, the metacercariae in the fish host came to a state of maturity and beyond this stage some metacercariae started the process of degeneration and extinction in as early as 30 days, and as more days elapsed, mortality of the metacercariae was not uniformly increased but difference of mortality appeared to be according to the individual of fish host. That is, in 390, 540 and 586 days, all of the metacercariae in the fish hosts became dead, meanwhile almost all of those found in the fish host of 596 days after the infection survived (mortality; 8.51 percent). Percentage of orally administered metacercariae developing to maturity in rabbit is 10.46 percent in the last case. As the days were progressed the shapes of the metacercariae in the fish host tended to change from ellipsoid to almost round shapes, the length became shorter while the width was wider. The results shown above revealed that C. eigenmanni was, though it could not be proper host than P. parva, suitable as the second intermediate host in addition to our previous observation results.
parasitology-helminth-trematoda ; Clonorchis sinensis ; epidemiology ; Cultriculus eigenmanni ; metacercaria ; intermediate host

Six metacercariae were found from the gill filaments of Conger myriaster purchased at Mokpo City in Korea on 7 September 1996. Based on the morphology of the excysted specimen, we identified them as metacercariae of Heterophyopsis continua. C. myriaster is a new intermediate host of H. continua in the literature.
parasitology-helminth-trematoda ; Heterophyopsis ontinua ; metacercaria ; intermediate host ; epidemiology ; Conger myriaster

One hundred and two stray dogs in Ejungbu City of Kyunggi-Do, Korea were examined to reveal out the degree of natural helminthic infection of small intestine. Helminthes were collected at autopsy, by scraping the intestinal contents. The collected worms were classified by their morphological characteristics. Out of 102 examined, 72 dogs were infected with any helminthes. The common helminthes were Dipylidium caninum (47 percent), Ancylostoma caninum (26 percent), Toxascaris leonina (16 percent) and Toxocara canis (13 percent). Taenia pisiformis (9 percent), Echinostoma hortense (4 percent), E. cinetorchis (2 percent), Spirometra mansoni (2 percent) were also found. One dog was incidentally found to be infected with Clonorchis sinensis. The prevalence of Toxascaris leonina was relatively high in this study over Toxocara canis, and its significance was discussed. Dogs were firstly described as the reservoir hosts of Echinostoma hortense and E. cinetorchis in Korea.
parasitology-helminth-nematoda-trematoda ; cestoda ; dog ; epidemiology ; morphology ; Dipylidium caninum ; Ancylostoma caninum ; Toxascaris leonina ; Toxocara canis ; Taenia pisiformis ; Echinostoma hortense ; Echinostoma cinetorchis ; Spirometra mansoni ; reservoir host ; intermediate host