It was discovered by British physician James McConnell at the Medical College Hospital in Calcutta (Kolkata) in 1874.

[2] The infection, called clonorchiasis, generally appears as jaundice, indigestion, biliary inflammation, bile duct obstruction, and even liver cirrhosis, cholangiocarcinoma, and hepatic carcinoma.

The earliest record is from corpses buried in 278 BC at Jiangling County of Hubei Province and the Warring States tomb of the western Han Dynasty.

The parasite was discovered only in 1874, though, by James McConnell, a professor of pathology and resident physician at the Medical College Hospital in Calcutta.

On autopsy, he observed that the corpse had a swollen liver (hepatomegaly) and distended bile ducts, which he noted were blocked by "small, dark, vermicular-looking bodies."

[7] The formal scientific description was published in 1875 by Thomas Spencer Cobbold, who named it Distoma sinense.

Erwin von Baelz reported the presence of similar flukes from an autopsy of a Japanese patient at Tokyo University in 1883.

Further analyses by Arthur Looss, though, showed significant differences from the general features of Opisthorchis, particularly on the highly branched testes.

In 1912, Harujiro Kobayashi corrected the classification that the differences in sizes were due to the nature of the host and intensity of infection, and had nothing to do with the biology.

[10] It narrows at the anterior region into a small opening called the oral sucker, which act as the mouth.

Other highly branched organs called vitellaria (or vitelline glands) are distributed on either side of the body.

[12] Freshwater snail Parafossarulus manchouricus often serves as a first intermediate host for C. sinensis in China, Japan, Korea, and Russia.

This aids the fluke in reproduction, because it enables the miracidium to capitalize on one-chance occasion of passively being eaten by a snail before the egg dies.

[11] The common second intermediate hosts are freshwater fish such as common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idellus), crucian carp (Carassius carassius), goldfish (Carassius auratus), Pseudorasbora parva, Abbottina rivularis, Hemiculter spp., Opsariichthys spp., Rhodeus spp., Sarcocheilichthys spp., Zacco platypus, Nipponocypris temminckii, and pond smelt (Hypomesus olidus).

[21] Other definitive hosts are fish-eating mammals such as dogs, cats, rats, pigs, badgers, weasels, camels, and buffaloes.

[3][7][4] Infection rates are generally higher in men, fishermen, farmers, businessmen, and catering staff.

More cases occur in low- or middle-class countries, increasing the disease burden and creating economic problems.

The calculated economic burden for treating clonorchiasis-related ailments in the Guangdong Province of China alone was $200 million by 2010.

Commonly eaten fishes (e.g. C. idellus, C. auratus, H. nobilis, C. carpio, H. molitrix, and M. anguillicaudatus) were found to have the metacercariae when sampled from lakes, rivers, and markets.

[22] Dwelling in the bile ducts, C. sinensis induces an inflammatory reaction, epithelial hyperplasia, and sometimes even cholangiocarcinoma, the incidence of which is raised in fluke-infested areas.

is the possibility for the adult metacercaria to consume all bile created in the liver, which would inhibit the host human from digesting food, especially fats.

[citation needed] Unusual cases of liver abscesses due to clonorchiasis have been reported.

Long-standing infections consist of fatigue, abdominal discomfort, anorexia, weight loss, diarrhea, and jaundice.

[25] Infection is detected mainly on identification of eggs by microscopic demonstration in faeces or in duodenal aspirate, but other sophisticated methods have been developed, such as ELISA, which has become the most important clinical technique.

Traits that raise suspicion for the infection include intra- and extrahepatic dilatation and structures with intraductal pigmented stones, usually in the absence of gallstones and with regions of segmental liver atrophy, particularly the lateral aspect of the left hepatic lobe.

[26] Drugs used to treat infestation include triclabendazole, praziquantel, bithionol, albendazole, levamisole, and mebendazole.