• Parasites, Hosts and Diseases
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• v.31 no.3
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• pp.183-192
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• 1993

A transmission electron microscopic study was performed to observe the ultrastructures of the male germinal cells and spermatozoa of Fibricola seoulensis. Spermatogonia were found in the periphery of the testis and characterized by large nuclei and comparatively little cytoplasms. Spermatocytes contained an oval to spherical nucleus. Their nuclear volume was little larger in comparative to that of cytoplasm, and the chromatin was comparatively little. The early spermatids were characterized by a great amount of cytoplasm, and numerous mitochondria encircled the nucleus. In a more advanced spermatids the electron-dense strands of chromatin appeared in the nucleus, and a pair of rootlet of the axoneme and a microtubule-organizing center (MTOC) were observed near the nucleus. The sectioned spermatozoa were found in the testis and the seminal vesicle. Their cross sectional views were divided into 6 types when they were distinguished on the basis of the morphology and components. The spermatozoa of F. seoulensis showed two flagella of 9+1 type axoneme.

• Parasites, Hosts and Diseases
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• v.31 no.4
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• pp.321-330
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• 1993

F. seoulensis were obtained from artificially infected albino rats at 3, 4, 5, 6, 7 days after infection. The worms and metacercariae were washed in physiological saline solution, and fled with 10% neutral formalin. The acetylcholinesterase (AchE) stained by one histochemistry using acetylthiocholine iodide as substrate. Eserine, ism-OMPA and BW284C51 were used as inhibitors of AchE. The nervous system consists of three pairs longitudinal nerve trunks interconnected with excretory plexus in posterior half, and phinmc and oral sucker in anterior half of metacercariae and adults. The longitudinal nerve trunks are interconnected with transverse commissures and numerous circular commissures. Considerable numbers of circular commissures are interconnected with longitudinal nerve trunks tying on the surface of the worms. At each stage of juvenile worms, AchE and nonspecific cholinesterase activites were observed in the oral sucker, ventral sucker, pharynx and nerve system. Isoxymes of AchE in f seoderuts were separated into the two bands, 69 kDa and 132 kDa. The major band was 69 kDa.

• Parasites, Hosts and Diseases
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• v.26 no.3
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• pp.179-188
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• 1988

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 acute 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 fame 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. seoulensis and found that it is possible to maintain the life cycle in the laboratory.

• Parasites, Hosts and Diseases
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• v.31 no.2
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• pp.109-116
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• 1993

Worm recovery rates and pathologic changes in small intestine of albino rats were observed after concurrent and challenge infections with metacercariae (MCI of Fibricota seouLensis and MetaBonimus vokogaupci, and compared with those of single Infection groups. Albino rats In concurrent Infection group were killed 20 days after feeding with 1,000 MC of each fluke. Rats in challenge. infection group were fed with 1.000 MC of f seouleni,s and challenged by 1,000 MC of M. yokogawai 10 days after primary infection, then killed 10 days thereafter. In concurrent infection group, mean number of F. seoulensis and M. yokogawai recovered, 250 and 118 respectively, were similar to those of single infection groups. However, more flukes were collected from the duodenum and less flukes were from the ileum than from single infection group. In challenge Infection group, the recovery rate of F. seoulensis was similar to that of sin91e infection group and the distribution of thIn flukes was similar to that of concurrent infection group. Mean number of M. yokogculat, 69, was signiflcantly lower than that of single infection group. Its distribution, however, extended to the duodenum and most of the flukes were recovered from the jejunum. In concurrent infection group, villi of the duodenum were more markely thickened, fused and shortened than those in F. seoulensis sing1e Infection group. The crypt epithelium appeared to be hyperplastic and inflammatory cell infiltration into the villous stroma was mild. Villous atrophy in the jrlunum and ileum was ndlder than in M. yokogawai single infection group. In challenge Infection group, the fhldlngs were simuar to those of concurrent Infection group. Crypt epithelium hyperplasla was not severe in duodenum. Inflammatory reaction was observed in submucosa of the Jrjunum and ileum. From the above results, it Is considered that F. seoulenis ikabiting in upper part of small intestine affect the settlement of M. yokoguwai introduced later In lower part of the intestine.

• Parasites, Hosts and Diseases
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• v.31 no.4
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• pp.315-320
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• 1993

We observed ultra-structure of the tribocytic organ of Firicola seoulensis with transmission electron microscope. Microvilli are observed on the surface of the tribocytic organ. Below the muscle layer, we can find three types of cells. Type I cell has electron lucent cytoplasm with a few granules, while type II cell shows electron dense cytoplasm and the particulate granules. Type III cell's electron dense cytoplasm possesses many granules. Of the above three cells, Type I and II cells are believed as tegumental cells. Type III cells are thought as glandular cells specific to the tribocytic organ. This finding on also explain the secretory function of the tribocytic organ of f seoulensis.

• Parasites, Hosts and Diseases
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• v.26 no.1
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• pp.45-54
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• 1988

To observe the clinical course and intestinal histopathology in heavy infection of Fibricola seoulensis, an experimental study was performed in mice. Clinical, experimental infection with 1, 000 metacercariae. On the 11th day after infection, the mice began to die and all of the infected mice were dead by the 16th day. The infected mice showed gradual weight loss. Occult blood was detected after the 10th day. Diarrhea accurred after the 9th day and was recognized in all of the infected mice on the 12th day. Hemoglobin and mean corpuscular hemoglobin decreased significantily after the 12th day, and mean corpuscular hemoglobin concentration decreased in all infected mice. The histopathological changes were more marked in the duodenum than in the jejunum or ileum. Major changes were villous atrophy and crypt hyperplasia, with decreased villus/crypt ratio, inflammatory cell infiltration and stromal edema. The present results suggest that the cause of death of mice heavily infected with F. seoulensis should be malnutrition and severe fluid loss due to malabsorption, together with intestinal bleeding.

• Parasites, Hosts and Diseases
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• v.27 no.4
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• pp.249-252
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• 1989

Fibricola cratera is a strigeoid trematode indigenous to North America that, heretofore, was known only to infect wild mammals. Herein, it is reported that an experimental inoculation of a human volunteer produced a patellt infection that lasted 40 months. Symptoms of epigastric discomfort, loose stools and flatulence occurred over the first year of infection and ameliorated thereafter. Eggs per gram of stool were low (${\leq}2$) throughout the course of infection and were not detected by the standard technique of formalin-ether concentration. To monitor infection, the entire stool sample was examined each month after sieving through No. 10 (pore size 2 mm) and 100 (pore size $145{\;}{\mu\textrm{m}}$) sieves and collecting eggs on a No. 325 (pore size $45{\;}{\mu\textrm{m}}$) sieve. This is the first report of a North American strigeoid trematode capable of maturing in a human and is only the second species of strigeoid known to do so. The other species is F. seoulensis which has been implicated in 26 human infections in Korea.

• Parasites, Hosts and Diseases
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• v.21 no.2
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• pp.224-233
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• 1983

An experimental study was carried out to observe the susceptibility of several kinds of laboratory animals to Fibricola seoulensis infection, a diplostomatid fluke of mammals. The metacercariae were obtained from the viscera of the snakes, Natrix tigrina lateralis and 50~2,000 in number each was artificially fed to a total of 127 animals; albino rats, mice, dogs, cats, rabbits and chickens. After 3 days to 8 weeks the animals were sacrificed and the recovery rate of worms as well as their maturity was observed. The results are as follows: 1. The overall worm recovery rates throughout the experimental period was highest in albino rats (40.0%) followed by mice (33.9%), cats (20.9%), dogs (11.4%), rabbits (0.05%) and chickens (0%). However, the recovery rates in the same host decreased as infection progressed longer and variable by the amount of metacercariae given. 2. From albino rats and mice, the highest recovery rates were obtained in 1,000 and 200-metacercariae infection groups respectively, and it is considered that such amount should be the optimum dose for experimental infection of these animals. 3. The main location of F. seoulensis in experimental animals was small intestine especially the duodenum. 4. The maturity index (No. mature worms/ No. examined) was 100% in albino rats and mice, while only 22.7% or 0% in dogs or cats respectively. From the results, it is concluded that albino rats and mice are the most susceptible hosts for F. seoulensis infection among six kinds of laboratory animals examined.

• Parasites, Hosts and Diseases
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• v.27 no.1
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• pp.35-40
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• 1989

It is well known that the duodenum of mice or rats infected with Fibricoln seoulensis shows atrophy of villi (shortening, blunting, widening, fusion) and hyperplasia of crypts. This study was performed to observe healing process of .these pathological changes after deworming with anthelmintic treatment. Albino rats infected each with.1,000 metacercariae of F. seeulensis were treated with single dose of 10 mg/kg praziquantel on day 15 post·infection. On day 1, 3, 5, 7, 15, 21 and 28 after the treatment, they were sacrificed and their duodenums were histopathologically studied. Control (uninfected) rats showed their normal finger-like projections of duodenal villi and well arranged crypts. In comparison, untreated (infected) contiols revealed severe mucosal changes characteristic of villous atrophy and crypt hyperplasia in their duodenum. The damaged duodenal mucosa was found to restore its normal morphology after praziquantel treatment; until day 3 post-treatment the mucosa was severely atrophied; on day 5 long and slender villi sometimes appeared among the fused and stout ones; after day 15 the villi were in their normalising process. From this experiment, it was shown that the mucosal changes in the duodenum of rats caused by F. seoulensis infection were completely reversible in 21∼28 days after anthelmintic treatment.

• Parasites, Hosts and Diseases
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• v.22 no.1
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• pp.61-65
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• 1984

A mass fecal examination was performed in Seoul, Korea from December 1983 to March 1984 and 15 egg positive cases of Fibricola seoulensis were discovered. They were treated with praziquantel($Distocide{\circledR}$) 20mg/kg single dose and magnesium salt for purgation. The adult worms of F. seoulensis were collected from 6 of them. The number of the flukes ranged 1-78 by the case. The cases had no clinical manifestation at all. They were all Korean males in twenties, and had the histories of eating the roast or raw snakes or frogs. Fibricoliasis is expected to be prevalent among the snake-eaters in Korea. Further cases will be detected by sedulous differentiation of thinshelled immature operculated eggs of 0.08~0.102mmn length. Praziquantel seems to be an excellent chemotherapeutic for fibricoliasis.