Encyclopedia of Parasitology

Living Edition
| Editors: Heinz Mehlhorn

Metagonimus Species

Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27769-6_1914-2

Keywords

Brackish Water Adult Worm Ventral Sucker Endemic Region Microscopical Determination 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Name

Greek: meta = behind; gone = sexual organ. Yokogawa = famous Japanese parasitologist and author. English: Spiny intestinal fluke or spiny dwarf worm.

Geographic Distribution/Epidemiology

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.

Morphology/Life Cycle

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.

Diagnosis

Microscopical determination of the small sized eggs (27 × 16 μm) by help of concentration methods (S.A.F.C., M.I.F.C., flotation). Since the eggs look very similar to Heterophyes heterophyes, a species determination based alone on eggs is impossible.

Infection

Oral uptake of metacercariae in raw or undercooked meat or fish.

Prophylaxis

Avoid to eat raw fish in endemic regions.

Incubation Period

1–3weeks.

Prepatent Period

1–2 weeks.

Patency

6–10 months.

Therapy

Drug of choice for humans is praziquantel (1 × 20 mg/kg bodyweight) (Fig. 1).
Fig. 1

Scanning electron micrograph of the ventral side of an adult worm showing the scaly surface and the laterally from the midline situated small ventral sucker (the sexual opening is situated close by in a fold)

Further Reading

  1. Cho SH et al (2011) Prevalence of Metagonimus metacercariae in sweetfish, Plecoglossus altivelis, from Eastern and Southern coastal areas in Korea. Korean J Parasitol 49:161–165CrossRefPubMedPubMedCentralGoogle Scholar
  2. Li MH et al (2010) Infectivity and development of Metagonimus yokogawai in experimentally infected domestic ducks (Cairina moschata). Vet Parasitol 168:45–50CrossRefPubMedGoogle Scholar
  3. Li MH et al (2013) Metagonimus yokogawai: metacercariae survey in fishes and its development to adult worms in various rodents. Parasitol Res 112:1647–1653CrossRefPubMedGoogle Scholar
  4. 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

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Institut für Zoomorphologie, Zellbiologie und ParasitologieHeinrich-Heine-UniversitätDüsseldorfGermany