• Parasites, Hosts and Diseases
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• v.31 no.2
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• pp.165-168
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• 1993

In order to know the enzyme activities of Filbricola seouzenis, an intestinal trematode of human and rodent in Korea. the enzyme histochemical method is applicated. Activities of acid phosphatase (E.C.3.1.3.2) and non-specific esterase (E.C.3.1.1) were present in microvilli and glandular cells of trlbocytic organ and the epithelium of the caecum.

• Parasites, Hosts and Diseases
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• v.28 no.3
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• pp.155-160
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• 1990

The tribocytic organ and tegument of Fibricola seeulensis were examined histochemically for the detection of carbohydrates, mucosubstances, amyloid, collagen and alkaline phosphatase. The surface, secretes, gland cells of the tribocytic organ, and the tegument of the worms were positive to periodic acid Schig (PAS) and PAS with diastase stain but negative to other stains. It was inferred that the tribocytic organ and tegument of F. seoulensis comprise neutral mucopolysaccharides, which may take a protective role against host enzymes. The surface and secretes of the tribocytic organ, and the tegument of the worms were also Positive to double bridge PAP for alkaline phosphatase. This fact suggests that they may play a role as both self protective and host tissue Iytic functions.

• Parasites, Hosts and Diseases
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• v.23 no.1
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• pp.47-58
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• 1985

An experimental study was performed to observe the in vivo effects of praziquantel on the light and scanning electron microscopic morphology of Fibricola seoulensis. The metacercariae were obtained from the snakes and 1, 000 in each number was orally given to total 15 albino rats; 5 controls and 10 treatment group. Seven days later the 10 rats were treated with 10 mg/kg praziquantcl and sacrificed 1~24 hours later to search for the worms from their small intestines. The major light microscopic changes in the drug-exposed worms were early contraction followed by relaxation of especially their forebody, vacuolization of the tegument and subtegumental parenchymal layers, and narrowing of the intestinal lumens. The scanning electron microscopic findings were characterized by formation of numerous blebs followed by rupture and subsequent destruction of their whole teguments. These results show that the change in worm body is not confined to the tegument but extends to deeper parenchymal portions and also occurs in their intestines. It is suggested that the drug uptake by the worms should be either through their tegument or through the digestive tract.

• 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.23 no.1
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• pp.41-46
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• 1985

The therapeutic effects 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 meta cercariae in number through intragastric tubes. One or four weeks la er the rats were treated with 1, 5, 10 or 20 mg/kg single dose of prazipuantel and sacrificed after 3 days or 10-120 minutes to search for the worms in their small intestine. The worm recovery rate at 3 days after the treatment was 10.7 % in 1 mg/kg dose group and o. 03~0.2% in 5, 10 and 20 mg/kg groups, 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 single dose. By observing the distribution pattern of worms in the small intestine after the treatment, dislodgement of the worms from the duodenum, their normal habitat, to the lower portions 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.

• 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.21-29
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• 1984

A scanning eletron microscopic study was performed to observe the tegumental surface of adult Fibricola seoulensis. The adult worms were collected from the small intestine of mice 5 days to 3 weeks after experimental infection with the metacercariae. The metacercariae were obtained from the viscera of the snakes, Matrix tigrina lateralis, by artificial digestion technique. The results were as follows: 1. The tegument of anterior body was covered with cobblestone-like cytoplasmic processes and that of posterior body showed finger-like processes. The posterior body had 4-5 large transverse wrinklings which formed many discontinued shallow rugae. 2. The entire surface of anterior body was regularly arranged with the spines of which tips diverged into 3 to 4 points. They were densely packed in anterior mid-median portion of dorsal surface where appeared a few spines indented upto 5 points. Farther laterally and posteriorly from this portion, the pointed spines were more sparse and became single tipped and extended to anterior one-third of posterior body, 3. The posterior surface of oral sucker was armed with 50-60 spines having 2-3 tips and ventral sucker also covered with such spines. On anteriormost dorsal surface arranged 60-70 spade-shaped spines. The tribocytic organ was armed with many stout recurved pile-like spines arranged radially. 4. There were 3 types of sensory papillae. The ciliated knob-like (Type I) papillae were almost bilaterally symmetrical in ventral and dorsal surfaces of anterior body, and abundant especially aroundbases of oral and ventral suckers, tribocytic organ, and in lateral margins of anterior body. About 24 non-ciliated round swellings (Type II) were observed around each lip of oral and ventral suckers. The plate-like elevated papilla without cilium (Type III) was found to distribute only in posterior body. These 3 types of papillae seem to be tangoreceptive and/or rheoreceptive in function when their morphology and distributions are considered.

• Parasites, Hosts and Diseases
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• v.26 no.2
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• pp.117-120
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• 1988

The egg laying capacity of Fibritola 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 1st 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.

• Parasites, Hosts and Diseases
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• v.24 no.2
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• pp.109-114
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• 1986

In order to observe the growth and development of Fibricola seoulensis metacercariae, the tadpoles of Rana nigromaculata were experimentally infected with the cercariae. The meta cercariae 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. 1. All of the tadpoles exposed to the cercariae were observed to harbour the larvae in their abdominal cavity. 2. The young metacercariae of 2 days after infection were $121.1{\mu}m$ long and $63.3{\mu}m$ wide. They grew linearly for the first 14 days to be $262.0{\mu}m$ long and $166.4{\mu}m$ wide. Thereafter, no more growth recognized until 65 days. 3. The larvae of 2 days old were similar with cercarial body and had 2 suckers, a pharynx, 2 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. 4. The metacercariae younger than 10 days could not infect the mice. Only the metacercariae older than 14 days had infectivity. The recovery rates 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 indispensable 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.

• 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.