Clonorchiasis

Clonorchis sinensis Life Cycle

Image

Image from the Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria.

Adult forms of C. sinensis live in the bile ducts. Eggs are passed in the feces and ingested by snails. Cercariae (free-swimming larvae) released from infected snails subsequently infect a variety of freshwater fish and shrimp. Humans can become infected by eating raw, undercooked, wine-soaked, dried, salted, or pickled fish, or less commonly freshwater shrimp, containing encysted metacercariae (resting or maturing stage). Metacercariae are released in the duodenum, enter the common bile duct through the ampulla of Vater, and migrate to smaller intrahepatic ducts (or occasionally the gallbladder and pancreatic ducts), where they mature into adults in about 1 month. The adults may live ≥ 25 years and grow to about 10 to 25 mm by 3 to 5 mm. For example, some U.S. Vietnam veterans have had serologic evidence of exposure to liver fluke infection when tested 5 decades after the war ended, but none had detectable liver fluke parasites by fecal examination (1).

Symptoms are related to worm burden; most infections are of light burden and asymptomatic. Symptoms typically occur in patients with a greater worm burden and longer duration of infection. Clinical manifestations typically occur as a result of inflammatory processes causing intermittent obstruction of the biliary ducts or mechanical injury resulting from worms feeding on mucosal tissue, toxic effects of the worms’ metabolic products, and secondary bacterial infections (1).

In the acute phase, heavier infections can cause fever, chills, epigastric pain, tender hepatomegaly, mild jaundice, and eosinophilia. Later, diarrhea may occur. Symptoms usually last for 2 to 4 weeks.

In heavy infections, chronic cholangitis may progress to atrophy of liver parenchyma and portal fibrosis. Jaundice may occur if a mass of flukes obstructs the biliary duct.

Other complications include suppurative cholangitis, cholelithiasis, cholecystitis, pancreatitis, and, late in the course, cholangiocarcinoma (bile duct cancer [2]). Vietnam veterans who develop cholangiocarcinoma may have been infected with Clonorchis sinensis or Opisthorchis viverrini while they served in Southeast Asia (3). The mortality risk of cholangiocarcinoma is increased in Asian people and in men who are older (4).

• Microscopic examination of feces

• Sometimes blood tests

• Sometimes imaging (abdominal radiographs, CT, MRI, or ultrasound)

• Rarely histopathological examination

Diagnosis of clonorchiasis is based on finding eggs in the feces or duodenal contents (feces ova and parasite examination). Eggs typically become detectable in the feces only 3 to 4 weeks after infection. The eggs are difficult to distinguish from those of Opisthorchis. Eggs cannot be detected in feces during biliary obstruction because they are primarily excreted via bile into the duodenum.

Clonorchis sinensis Egg

Image

CDC/DPDx

Other tests are nondiagnostic but may be abnormal; alkaline phosphatase and bilirubin may be elevated. High levels of circulating eosinophils and serum IgE are also common. Eosinophilia distinguishes liver fluke infection from acute viral hepatis.

A plain abdominal radiograph may occasionally show intrahepatic calcification. Hepatic ultrasound, CT, MRI, endoscopic retrograde cholangiopancreatography (ERCP), or cholangiography may show ductal irregularities and evidence of scarring.

Ultrasound screening for periductal fibrosis in high-risk patients (male, > 50 years old) in endemic areas can improve early detection of cholangiocarcinoma and thus survival rate (1).

Rarely, the diagnosis is confirmed by identifying adult flukes in histopathological examination of surgical specimens or by doing percutaneous transhepatic cholangiography; adult flukes may also be present in feces following anthelminthic therapy.

Organism-specific serologic, molecular (eg, polymerase chain reaction [PCR]) or antigenic (eg, enzyme-linked immunosorbent assay [ELISA]) methods of detection have been developed but are not widely available.

• Praziquantel or albendazolePraziquantel or albendazole

Treatment of clonorchiasis is with one of the following:

• Praziquantel orally 3 times a day for 2 daysPraziquantel orally 3 times a day for 2 days

• Albendazole orally once a day for 7 daysAlbendazole orally once a day for 7 days

Praziquantel shows high efficacy against clonorchiasis (Praziquantel shows high efficacy against clonorchiasis (1). Tribendimidine is a promising anthelmintic alternative to praziquantel, demonstrating similar cure rates and fewer gastrointestinal adverse effects when administered orally daily for 3 days, but it remains largely unavailable outside China. Praziquantel is the only medication recommended for global use by the World Health Organization. , demonstrating similar cure rates and fewer gastrointestinal adverse effects when administered orally daily for 3 days, but it remains largely unavailable outside China. Praziquantel is the only medication recommended for global use by the World Health Organization.

In the United States, the Centers for Disease Control and Prevention (CDC) recommends that albendazole may be used as an alternative agent. In the United States, the Centers for Disease Control and Prevention (CDC) recommends that albendazole may be used as an alternative agent.Albendazole additionally requires dosing over several days (typically 7 days). In one network meta-analysis, studies have indicated similar efficacy (ie, cure rates) for albendazole as for praziquantel; however, the studies on albendazole are limited by low sample sizes and a high risk of bias (additionally requires dosing over several days (typically 7 days). In one network meta-analysis, studies have indicated similar efficacy (ie, cure rates) for albendazole as for praziquantel; however, the studies on albendazole are limited by low sample sizes and a high risk of bias (1).

Biliary obstruction may require surgery.

Prevention of clonorchiasis involves thoroughly cooking freshwater fish and shrimp from endemic waters and not eating them raw, undercooked, dried, pickled, or wine-soaked. In endemic areas, mass treatment with praziquantel reduced clonorchiasis burden (Prevention of clonorchiasis involves thoroughly cooking freshwater fish and shrimp from endemic waters and not eating them raw, undercooked, dried, pickled, or wine-soaked. In endemic areas, mass treatment with praziquantel reduced clonorchiasis burden (2). Family members of infected patients should be evaluated for infection with feces microscopy for ova and parasites and blood count for eosinophilia.