'''''Clonorchis sinensis''''' est un ver responsable d'une distomatose humaine, la '''clonorchose'''.
<br>'''''La douve de Chine''''', ''Clonorchis sinensis'', est un ver de petite taille, parasite normal du porc, du chien et du chat qui, par sa présence chez l'homme, entraîne la '''distomatose hépatique d'Extrême-Orient'''.

==Répartition géographique et importance==

Le clonorchose est la parasitose hépatique la plus fréquente du monde. Elle est endémique en Extrême-Orient. Son importance tient autant de la forte proportion des atteintes (40 % de la population en moyenne, 100 % dans certains foyers) qu'à leur gravité habituelle en zones d'endémie où les réinfestations sont constantes.

==Morphologie==

L'adulte, très plat et translucide, est lancéolé arrondi à l'arrière, rougeâtre et mesure 10 à 20 mm de long.

==Biologie==

Accumulés par centaines ou par milliers dans les canaux biliaires, ces adultes, pendant 25 ou 30 ans, pondent des oeufs caractéristiques : petites amphores de 27 sur 16 microns, avec clapet bordé d'un anneau et pointe postérieure, qui sont éliminés par la bile puis les selles. Le cycle est à deux hôtes intermédiaires : un escargot (mollusque aquatique du genre bythinia) et un poisson cyprinidé (poisson rouge) dont les muscles hébergent les métacercaires infectieuses enkystées. La contamination de l'homme se fait par ingestion de poisson cru ou mal cuit. Le cycle est bouclé quand les jeunes douves ont gagné les voies biliaires.

{{Taxobox
| name = Human liver fluke
| regnum = Animalia
| phylum = Platyhelminthes
| classis = Trematoda
| ordo = Opisthorchiida
| familia = Opisthorchiidae
| genus = '''''Clonorchis'''''
| species = '''''sinensis'''''
| binomial = ''Clonorchis sinensis''
| binomial_authority = Looss, 1907
}}
<gallery>
Image:Clonorchis.jpg|Clonorchis sinensis under a light microscope.  Notice the ovaries.  This one is female.
</gallery>
The '''''Clonorchis sinensis''''' is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile. These animals, which are believed to be the third most prevalent worm parasite in the world, are endemic to Japan, China, Taiwan, and Southeast Asia, currently infecting an estimated 30,000,000 humans.

== Life cycle ==
left|thumb|280px|Life cycle of ''C. sinensis''

The egg of a ''Clonorchis sinensis'' (commonly: human liver fluke), which contains the miracidium that develops into the adult form, floats in freshwater until it is eaten by a snail'''

Once inside of the snail body, the miracidium hatches from the egg, and parasitically grows inside of the snail. The miracidium develops into a sporocyst, which in turn house the asexual reproduction of redia, the next stage. The redia themselves house the asexual reproduction of free-swimming cercaria. This system of asexual reproduction allows for an exponential multiplication of cercaria individuals from one miracidium. This aids the Clonorchis in reproduction, because it enables the miracidium to capitalize on one chance occasion of passively being eaten by a snail before the egg dies.

Once the redia mature, having grown inside the snail body until this point, they actively bore out of the snail body into the freshwater environment. There, instead of waiting to be consumed by a host (as is the case in their egg stage), they seek out a fish. Boring their way into the fish's body, they again become parasites of their new hosts. 

Once inside of the fish muscle, the cercaria create a protective metacercarial cyst with which to encapsulate their bodies. This protective cyst proves useful when the fish muscle is consumed by a human. The acid-resistant cyst enables the metacercaria to avoid being digested by the human gastric acids, and allows the metacercaria to reach the small intestine unharmed. Reaching the small intestines, the metacercaria navigate toward the human liver, which becomes its final habitat. ''Clonorchis'' feed on human bile created by the liver. In the human liver, the mature ''Clonorchis'' reaches its stage of sexual reproduction. The hermaphroditic adults produce eggs every 1–30 seconds, resulting in the rapid multiplication of inhabitants in the liver.