Chinese Liver Fluke

Clonorchis sinensis

''Clonorchis sinensis'', the Chinese liver fluke, is a liver fluke belonging to the class Trematoda, phylum Platyhelminthes. It infects fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding on bile. It was discovered by British physician James McConnell at the Medical College Hospital in Calcutta in 1874. The first description was given by Thomas Spencer Cobbold, who named it ''Distoma sinense''. The fluke passes its lifecycle in three different hosts, namely freshwater snail as first intermediate hosts, freshwater fish as second intermediate host, and mammals as definitive hosts.

Endemic to Asia and Russia, ''C. sinensis'' is the most prevalent human fluke in Asia and third-most in the world. It is still actively transmitted in Korea, China, Vietnam, and Russia. Most infections occur in China. The infection, called clonorchiasis, generally appears as jaundice, indigestion, biliary inflammation, bile duct obstruction, and even liver cirrhosis, cholangiocarcinoma, and hepatic carcinoma.

As a major causative agent of bile duct cancer, the International Agency for Research on Cancer has classified ''C. sinensis'' as a group 1 biological carcinogen in 2009.
Chinese Liver Fluke - Clonorchis sinensis Chinese liver flukes infect fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding on bile. The fluke passes its lifecycle in three different hosts (freshwater snails as first intermediate hosts, freshwater fish as second intermediate host, and mammals as definitive hosts). Infection causes jaundice, indigestion, biliary inflammation, bile duct obstruction, liver cirrhosis, cholangiocarcinoma, and hepatic carcinoma. *cross-section microscope slide Clonorchis,Clonorchis sinensis,Geotagged,Trematoda,United States,Winter,chinese liver fluke,fluke,liver fluke

Appearance

An adult ''C. sinensis'' is a flattened and leaf-shaped fluke. The body is slightly elongated and slender, measuring 15–20 mm in length and 3–4 mm in width. It narrows at the anterior region into a small opening called the oral sucker, which act as the mouth. From the mouth, two tubes called caeca run the length of body. They are the digestive and excretory tracts. The posterior end is broad and blunt. A poorly developed ventral sucker lies behind the oral sucker, at about one-fourth of the body length from the anterior end. A common genital pore opens just in front of it. As a hermaphrodite, it has both male and female reproductive organs. A single rounded ovary is at the centre of the body, and two testes are towards the posterior end. The uterus from the ovary, and seminal ducts from the testes, meet and open at the genital pore. The testes are highly branched. Other highly branched organs called vitellaria are distributed on either side of the body.

The eggs are similar to those of other related flukes such as ''Opisthorchis viverrini'' and ''O. felineus'', and are often confused during diagnosis. They small and oval in shape, measuring about 30 x 15 μm in diameter. They are sharply curved and with a clear convex operculum towards the narrower end. At the broader end is a stem-shaped knob. The miracidium can be seen inside the fertilised egg.

Reproduction

The eggs of a ''C. sinensis'' are released through the biliary tract, and excreted out along with the faeces. The eggs are embryonated and contain the larvae called miracidia. Unlike most other flukes in which the miracidia undergo development and swim in water to infect suitable host, the eggs of ''C. sinensis'' are simply deposited in water. The eggs are then eaten by snails.

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Taxonomy
KingdomAnimalia
DivisionPlatyhelminthes
ClassTrematoda
OrderPlagiorchiida
FamilyOpisthorchiidae
GenusClonorchis
SpeciesC. sinensis
Photographed in
United States of America