The egg laying capacity of Fibricola seoulensis was observed in mice and rats. In mice, the mean number of eggs produced by an adult worm a day was 116 at the first week after infection, 123 at the 2nd week and 42 at the 3rd week. Thereafter, the capacity of about 20 eggs/worm/day was maintained up to one year period. In rats, it generally produced more eggs; 49 at 1 week, 250 at 2 weeks, 216 at 4 weeks, 327 at 6 months and 11 at one year after infection. It survived longer than a year in mice and rats.
parasitology-helminth-trematoda ; Fibricola seoulensis ; egg

The pattern of sensory papillae, chaetotaxy, of the cercaria of Clonorchis sinensis was observed. The chaetotaxy was as follows; 5-6 Ci l, 4-5 Ci 2, 5-6 Ci 3 at lst row, 4 Cii 1, 2 Cii 2, 4 Cii 3, 5-6 Cii 4 at 2nd row, 3-4 Ciii 1, 2-3 Ciii 2 at 3rd row, and 2 Civ 1, 2-3 Civ 2, 2-3 Civ 3, at 4th row, in cephalic region; 2 AiV, l AiD, 2 AiiV, 1 AiiD, 2 AiiiV, 2 AiiiD, 1 AivV, 1 AivD, 1 PiiD, l PiiiD, in ventral(V) and dorsal(D) portions of body. Caudal region revealed 2-2-2-2 formula.
parasitology-helminth-trematoda ; Clonorchis sinensis ; cercaria

The present study was performed to observe the ultrastructure of the integument of adult Paragonimus westermani. Dogs experimentally infected with 60 metacercariae of P. westermani were autopsied 4 months after the infection. Adult P. westermani were extracted from the dogs and the fine structure was studied by means of scanning and transmission electron microscope. The findings are as follows: Scanning electron microscopic findings showed that the spines and the papillae are distributed at whole body surface but the well developed spines or papaillae are shown around the oral suckrer and ventral sucker. At the end of the body, excretory pore was found, the shape was irregular. Transmission electron microscopic findings showed that plasma membrane, tegument, basal lamina, connective tissue, circular muscle layer, longitudinal muscle layer, nerve axon and tegumental cell were observed. In higher magnification, plasma membrane and bar-shaped granules were found at the outer surface of the tegument.
parasitology-helminth-trematoda ; Paragonimus westermani ; electron microscopy

Adult Clonorchis sinensis were collected from the biliary passage of nine cases of medico-legal autopsies. The worms were washed repeatedly with tap water and rinsed twice with physiological saline. Incubation took place in Tyrode's medium in order to recover live worms. The number of worms surviving in the medium was determined. The rate of surviving worms showed an unexpectedly high percentage (22.8%) in those cases autopsied 2 days after death. The surviving worm burden dropped sharply to 6.3 and 9.2 percent for those samples taken 5 days after death.
parasitology-helminth-trematoda ; Clonorchis sinensis ; autopsy

In this study the authors examined the protein components at various stages of Clonorchis sinensis, and those of tegument and metabolite of adult Clonorchis by using SDS-polyacrylamide gel electrophoresis and immunodiffusion. The following results were obtained: The protein components of C. sinensis were gradually changed during its development. A considerable change occurred during the initial 7 days after the metacercarial infection. Two bands of protein of about 97,000 molecular weight (MW) and 178,000 MW were unique to excysted metacercaria of C. sinensis. Other 2 bands of protein of 23,000 and 25,000 MW which were absent in metacercariae, might be associated with the development of sex organs in adult. In the metabolite, some components of tegumental proteins were detected. And this tegumental protein components in metabolite seems to be the major antigenic components reacting with infected rabbit antiserum by immunodiffusion. Twenty bands of protein were detected in the isolated adult tegument. Among them 6 bands were in 97,000-65,000 MW, 3 bands in 56,000-53,000 MW and 5 bands in 37,000-30,000 MW. On the other hand, in metabolic products of adult C. sinensis, 17 bands were detected.
parasitology-helminth-trematoda ; Clonorchis sinensis ; biochemistry ; protein

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

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

The present study was undertaken to observe the morphological changes of Clonorchis sinensis obtained from experimentally infected rats treated with praziquantel (Biltricide) which is a new anthelmintic agent with high activity against a broad spectrum of cestode and trematode species. For this study, the rats were infected experimentally with about 50 metacercariae of C. sinensis and were given praziquantel a single dose of 600 mg per kg of body weight at 5 weeks after infection. The Clonorchis worms were isolated from the bile ducts of the rats which were autopsied on the 4th day after treatment. After isolation the parasites were observed their shape and motility in the medium of 37 C physiological saline solution, and then the fine structure of the tegument of C. sinensis was studied by means of light, scanning and transmission electron microscope. The findings of the observation were compared with those of untreated parasites. The results are as follows: All the isolated worms moved actively in the medium of physiological saline solution (37 C). A majority of the parasites obtained from the treated rats showed a large balloon shaped structure on the surface between oral and ventral suckers. But such structure has never seen in the parasites obtained from control rats. By the scanning electron microscopic observation, the regular pattern of the tegumental ridges was significantly changed on the outer surfaces of parasites obtained from the treated rats as compared with those of the control rats. By the transmission electron microscopic observation, the numerous mitochondriae in the syncytial tegumental layer of the treated parasites appeared to be degenerated and formed small vacuoles, and the tegumental ridges were also degenerated and showed somewhat flattened. In the parasites obtained from the treated rats, a different size of vacuoles interspersed in the distal part of the syncytial tegument and also in subepithelial region of the urinary bladder. These vacuoles are fused each other and lead to the disruption of the apical region of syncytial tegument along the basement layer. Finally the basement layer was dislocated. So that the tegumental layer appeared as a large balloon.
parasitology-helminth-trematoda ; Clonorchis sinensis ; chemotherapy

The therapeutic effect of praziquantel on Fibricola seoulensis infection were studied by experimental infection of albino rats with the metacercariae obtained from the snakes. Total 51 albino rats were infected each with 500 or 1,000 metacercariae in number through intragastric tubes. One or four weeks later the rats were treated with 1, 5, 10 or 20 mg/kg sigle dose of praziquantel and sacrificed after 3 days or 10-120 minutes to search for the worms in their small intestine. The worms recovery rate at 3 days after the treatment was 10.7% in 1 mg/kg does group and 0.03-0.2% in 5, 10 and 20 mg/kg group, while that of untreated control was 51.3%. The minimum effective dose to treat F. seoulensis infection in the rats is considered to be 5 mg/kg in sigle dose. By observing the distribution pattern of worms in the small intestine after the treatment, dislodgment of the worms froms the duodenum, thier normal habitat, to the lower portion was recognizable within as early as 10 minutes. The majority of worms was found to have descended to the ileo-caecal portion after 60-120 minutes.
parasitology-helminth-trematoda ; Fibricola seoulensis ; chemotherapy-praziquantel