KeywordsBrackish Water Adult Worm Ventral Sucker Endemic Region Microscopical Determination
Greek: meta = behind; gone = sexual organ. Yokogawa = famous Japanese parasitologist and author. English: Spiny intestinal fluke or spiny dwarf worm.
Mainly in East Asia, but also focally in Romania, Spain, Russia, and Israel. WHO estimates that about five to ten millions of humans are infected.
The adult worms (e.g., M. yokogawai) reach a size of 1–2.5 × 0.4–0.7 mm. Their tegument is covered with fine scales introducing a thorny aspect of the surface. Their ventral sucker is not situated exactly in the midline of the body but somewhat laterally displaced. Main hosts are fish eating birds (e.g., pelicans) or mammals (inclusive humans), in the intestines of which where the adult worms are attached at the walls of the small intestine. The operculated eggs (27 × 16 μm) are excreted with the feces. The miracidia are set free in fresh or brackish water and enter the skin of water snails of the genera Melania and Sulcospira. The excreted cercariae enter fresh water fish (e.g., trouts, carps) and become encysted as metacercariae.
Symptoms of Disease (Metagonimiasis)
Huge members of these very small worms may introduce severe diarrheas, but low graded infections are often symptomless.
Oral uptake of metacercariae in raw or undercooked meat or fish.
Avoid to eat raw fish in endemic regions.
- Mehlhorn H et al (1983) Ultrastructural investigations of the effects of praziquantel on human trematodes from Asia (Clonorchis sinensis, Metagonimus yokogawai, Opisthorchis viverrini, Paragonimus westermani, Schistosoma japonicum). Drug Res 33:91–98Google Scholar