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Korean J Parasitol > Volume 20(2):1982 > Article

Original Article
Korean J Parasitol. 1982 Dec;20(2):101-111. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1982.20.2.101
Copyright © 1982 by The Korean Society for Parasitology
Studies on intestinal trematodes in Korea VI. On the metacercaria and the second intermediate host of Fibricola seoulensis
Sung-Tae Hong,Sung-Jong Hong,Soon-Hyung Lee,Byong-Seol Seo and Je-Geun Chi*
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Korea.
*Department of Pathology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Korea.
Abstract

This study was carried out to confirm the infection source of the human case of Fibricola seoulensis, and to reveal out a part of its life cycle in Korea. Also the morphological characteristics of the metacercaria were described.

The results were summarized as follows:

1. Rana nigromaculata and Natrix tigrina lateralis were found to be infected naturally by the metacercariae(diplostomula) of F. seoulensis. The metacercarial capsule was round to elliptical in tissue of the intermediate hosts with a long diameter 0.232~0.385 mm. Liberated metacercariae were ovoid with small conical posterior body. Body length measured 0.199~0.312 mm and width 0.153~0.252 mm.

2. The infection rate of R. nigromaculata by the metacercariae ranged from 87% to 100% by area, and the number of the larvae ranged from 3 to 390 by frog. The metacercariae were found in skeletal muscle of frogs, from head to hindlegs.

3. All examined N. t. lateralis were found to be infected by the metacercariae with the range of numbers frome 3 to 35,918. The larvae were collected from all viscera and body segments except for the head of the snakes. However, a great majority of the metacercariae were collected from the stomach.

4. Hematoxylin-eosin stained preparations of frog skeletal muscle and snakes stomach revealed that the metacercariae had no cyst wall of worm origin, but encapsulated by the host tissue. Some of them were found in dilated lymphatic vessels. The larval infection was associated with slight or severe inflammatory reaction even with granuloma formation.

By above results, it was concluded that the frog, Rana nigromaculata, was the second intermediate host, and the snake Natrix tigrina lateralis was a paratenic host of F. seoulensis in nature in Korea.

Figures


Fig. 1
The localities where the frogs(●) and snakes(▲) were collected.


EXPLANATIONS FOR PLATE
Fig. 1. Macroscopic view of the metacercariae of F. seoulensis in snake omentum

Fig. 2. Low power view of the metacercaria of F. seoulensis in frog muscle, ×140

Fig. 3. The metacercaria of F. seoulensis obtained from a frog peritoneal cavity, unstained, ×280

Fig. 4. Liberated metacercaria of F. seoulensis from snake stomach, acetocarmine stained, ×280



EXPLANATIONS FOR PLATE
Fig. 5. Sectioned metacercaria of F. seoulensis in endothelium lined duct in frog skeletal muscle, ×120

Fig. 6. Low power view of cross sectioned stomach of a snake showing many larvae of F. seoulensis in submucosa, HE stained, ×40

Fig. 7. Magnified view of submucosa showing tissue reactions around the metacercariae of F. seoulensis, ×100

Fig. 8. A granuloma with many eosinophils in submucosa of snake stomach, ×200


Tables


Table 1
Measurements of 10 acetocarmine stained metacercariae of F. seoulensis from frogs and snakes in millimeters


Table 2
Infection rate of frogs by the metacercariae of F. seoulensis


Table 3
Infection status of Rana nigromaculata by metacercariae of Fibricola seoulensis in the surveyed areas


Table 4
Distribution of metacercariae of Fibricola seoulensis by the body portion of frogs


Table 5
The infection of snakes by the metacercariae of F. seoulensis


Table 6
The number of metacercariae of F. seoulensis by the organ of Natrix tigrina lateralis*


Table 7
The number of the metacercariae of F. seoulensis from the body segments of N. t. lateralis

References
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