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As Zerkarie or cercaria (from Greek he kérkos "tail") is defined as the larval form in the development cycle of certain parasites , the trematodes (flukes). In older works, cercaria, especially in the livers of farm animals, are also referred to as leech snails .

Cercariae and metacercariae

Cercariae have an oval body and a round tail. Mouth and abdominal suction cups, pharynx , intestines and nervous system are available, only the genital organs are missing . Cercariae leave the host, usually a snail , piercing its skin, shedding its oar tail and encysting itself as metacercariae in certain animals or plants. These metacercariae are taken up by the host and develop into adult animals in it, which begin to produce eggs ( generation change ).


Examples are the small liver fluke , the large liver fluke , lungworm ( Paragonimus westermani ) and the giant intestinal fluke ( Fasciolopsis buski ).

Also to be mentioned is the pair of leeches , whose distribution in the population of ancient Egypt was estimated at 70 percent. The infestation could be reduced by hunting the intermediate host (water snail) and by protecting the natural predators of the water snail, ibis and bald ibis .

The "duck flea" is (picked up while swimming in open waters by humans) a Zerkarie responsible for the frequent occurrence of bathing dermatitis , also English Schistosomendermatitis or cercarial dermatitis called, is responsible. Responsible parasites are Trichobilharzia ocellata or Schistosoma mansoni , which actually attack water birds. One of the often infested false hosts is humans. The cercaria occur particularly near the shore and cause skin irritation ( Weiherbeiß ). As a preventive measure, vigorous drying with a towel is recommended so that parasites that have only partially penetrated the skin are removed.


  1. The term leech snail was also used earlier for the snail (Limacidae), a family of slugs.

See also

Web links

Wiktionary: Zerkarie  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Jacob Christian Schaeffer: The leech snails in the livers of sheep and the sheep disease caused by these worms . Regensburg, Weiß 1753, 46 p., Archive.org
  2. J. Pilz, S. Eisele, R. Disko: Zerkariendermatitis (swimmer's itch). In: Der Hautarzt , Volume 46, No. 5, 1995, pp. 335-338.
  3. P. Horak, L. Kolarova: Cercarial dermatitis in Central Europe overview and current problems. In: Mitt Österr Ges Tropenmed. Parasitol , Volume 19, 1997, pp. 59-64.
  4. ^ Bathing dermatitis caused by cercaria in European inland waters . badegewaesser.niedersachsen.de; Retrieved on July 2, 2019 ("After bathing, the body should first be dried well, better rubbed off properly. Showering promotes the survival of the cercariae and penetration into the skin. It should therefore only follow a little later.")