Clonorchiasis: an update

Abstract

Clonorchis sinensis, the Chinese or oriental liver fluke, is an important human parasite and is widely distributed in southern Korea, China (including Taiwan), Japan, northern Vietnam and the far eastern part of Russia. Clonorchiasis occurs in all parts of the world where there are Asian immigrants from endemic areas. The human and animal reservoir hosts (dogs, pigs, cats and rats) acquire the infection from the ingestion of raw fish containing infectious metacercariae. The first intermediate snail hosts are mainly species of Parafossarulus and Bithynia. Numerous species of freshwater fish serve as the second intermediate hosts of C. sinensis. Extensive studies of clonorchiasis during several decades in Japan, Korea, China and other countries have shown much progress in proving its morphological features including ultrastructure, biology, pathogenesis, epidemiology, clinical manifestations and chemotherapy. The present review deals with mainly current results obtained on the epidemiological, pathological and clinical aspects, as well as control measures in endemic areas. As for the complications of clonorchiasis, formation of calculi in the intrahepatic biliary passages is one of the most characteristic pathological features. It is sometimes accompanied by suppurative cholangitis, cholecystitis, cholangiohepatitis and ultimately can cause cholangiocarcinoma. Experimental results on the relationship to the occurrence of cholangiocarcinoma are presented. Clinical diagnosis by radiological findings including cholangiography, sonography and computerized tomography as well as magnetic resonance imaging for biliary or pancreatic ducts are outlined. Current studies on immunology and molecular biology of C. sinensis were introduced. Praziquantel is the drug of choice for clonorchiasis. The most effective regimen is 25 mg kg(-1) three times daily (total dose, 75 mg kg(-1)) administered orally at 5- to 6-h intervals over a single day. Prevention and control measures are also discussed.

Microscopic Examination of Gallbladder Stones Improves Rate of Detection of Clonorchis sinensis Infection

“…In China, clonorchiasis prevails mainly in Guangdong, Guangxi, and Heilongjiang provinces. The main reason for this is the consumption of raw fish and crustaceans (1)(2)(3)(4). In the province of Guangdong, epidemiological surveys were carried out in 62 of 95 counties from 1997 to 2003.…”

Animal Reservoir Hosts and Fish-borne Zoonotic Trematode Infections on Fish Farms, Vietnam

“…We conclude that these domestic animals, especially dogs and pigs, play a major role in the epidemiology of FZT in aquaculture. Although reports from other Southeast Asian countries have suggested that nonhuman reservoir hosts play only a minor role in the epidemiology of liver fl ukes, specifi c studies on the role of reservoir hosts, other than ours, have not been carried out (1,13,14). One limitation of our study is that the use of 2 different methods to obtain prevalence data from humans (5) and domestic animals may have introduced a bias when comparing the relative contributions of the eggs to the environment.…”

Food-Borne Trematodiases

“…Biliary obstruction, intrahepatic stone formation, cholangitis, cholecystitis, cholelithiasis, biliary and liver abscesses, pancreatitis, and hepatitis are further severe symptoms. An increased risk of developing cholangiocarcinoma, a malignant tumor that arises from any portion of the bile ducts, is the most important clinical manifestation (58,85,91,92). C. sinensis has been classified by the International Agency for Research on Cancer (IARC) as a probable carcinogen (group 2A) (58).…”