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: 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. 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. 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. 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.
parasitology-helminth-trematoda ; Fibricola seoulensis ; metacercaria ; host ; frog ; Rana nigromaculata ; Rana rugosa ; Natrix tigrina lateralis ; Elaphae dione ; Dinodon rufozonatum rufozonatum ; Agkistrodon blomhoffi brevicaudus ; epidemiology

An investigation on the trematodes of Korean amphibians was carried out during the period from April to September of 1976. A total of 883 amphibians of 6 species were examined. These frogs, toads and salamanders were collected in the areas of the Han river side. And also these amphibians comprised 775 Rana nigromaculata, 53 Rana rugosa, 21 Hyla arborea japonica, 2 Bufo bufo gargarizans, 2 Gallula tornieri and 30 Hynobius leechi. Out of the results of this work, 7 species of trematodes belonging to 2 orders were found as follows: Monogenea: Diplorchis ranae Ozaki, 1931. Digenea: Diplodiscus japonicus (Yamaguti , 1936), Gorgodera japonica Yamaguti, 1936, Haematoloechus sibiricus japonicus(Yamaguti, 1936) , Mesocoelium brevicaecum Ochi, 1929, Loxogenes liberum Seno,1980, Pleurogenoides japonicus (Yamaguti, 1936).
parasitology-helminth-trematoda ; monogenea ; digenea ; epidemiology ; frog ; Rana nigromaculata ; Rana rugosa ; Hyla arborea japonica ; Bufo bufo gargarizans ; Gallula tornieri ; Hynobius leechi ; Diplorchis ranae ; Diplodiscus japonicus ; Gorgodera japonica ; Haematoloechus sibiricus japonicus ; Mesocoelium brevicaecum ; Loxogenes liberum ; Pleurogenoides japonicus