Studies on intestinal trematodes in Korea XIII. Two cases of natural human infection by Heterophyopsis continua and the status of metacercarial infection in brackish water fishes.

Two cases of natural human infection by Heterophyopsis continua (Heterophyidae) were identified by collection of adult worms in 1983 in Korea. And in order to know the source of infection a study on fish intermediate hosts was performed along the southwestern coastal areas. The cases were 24 and 50-year old males residing in southern coastal areas. They had the clinical complaints of non-specific gastrointestinal symptoms such as epigastric pain and one of them also complained the discharge of tapeworm segments. Praziquantel in single dose of 10~15 mg/kg was given followed by purgation with mangnesium salt and 2 and 46 specimens of H. continua were collected from the diarrheal stools. They said to have eaten raw flesh of several kinds of brackish water fishes. The results of fish examination for metacercarial infection were as follows: Seventeen (63.0%) out of 27 perches (Lateolabrax japonicus) and 10 (29.4%) out of 34 gobies (Acanthogobius flavimanus) harboured the metacercariae but none of 42 mullets (Mugil cephalus) were found to harbour them. The average metacercarial density in perches was 55.4 and 18.7 per fish respectively. And the majority of the metacercariae were collected from the muscle of body portions in these fishes. After the metacercariae were experimentally fed to two rats and one young dog, two adult worms were recovered from the dog while none from the rats. These worms were also indentified as H. continua. From the results it was concluded that the brackish water fishes which the human cases said to have eaten were the source of infection.