Clonorchiasis
Clonorchiasis is an infection of the biliary ducts of the liver caused by the parasite Clonorchis sinensis, commonly known as the Chinese liver fluke. This infection is primarily endemic to several regions in Asia, including South Korea, Japan, Taiwan, China, Vietnam, and eastern Russia, with occasional cases reported in other parts of the world such as Eastern Europe, Africa, and Latin America. People typically become infected by consuming raw, dried, or undercooked freshwater fish or crayfish that harbor the parasite.
While many individuals may not exhibit symptoms, more significant infections can lead to symptoms such as fever, abdominal pain, nausea, and jaundice. Long-term infections pose serious health risks, including cholangiocarcinoma, a type of cancer affecting the biliary duct system. Diagnosis usually involves a medical history review, stool sample analysis for the fluke's eggs, and imaging tests. Treatment is primarily managed with medications such as praziquantel or albendazole, which are effective in killing the flukes. Preventive measures focus on avoiding consumption of raw or undercooked fish from endemic regions, highlighting the importance of thorough cooking to ensure safety.
Clonorchiasis
Anatomy or system affected: Gastrointestinal system, intestines, liver,stomach
Definition
Clonorchiasis is an infection of the biliary ducts of the liver caused by the parasite Clonorchis sinensis, also known as the Chinese liver fluke. Infection with this liver fluke (trematode) is endemic to Asia, particularly in South Korea, Japan, Taiwan, China, Vietnam, and eastern Russia, and is also found in Eastern Europe, Africa, and Latin America. It is introduced occasionally in other countries such as the United States through contaminated food imported from Asia.
Causes
Humans become infected by C. sinensis by eating raw, dried, salted, or pickled fresh-water fish that contain the parasite. Immature flukes are released into the duodenum and ascend the common biliary tract through the ampulla of Vater. The flukes mature to adults in approximately one month and reside in the small- and medium-size intrahepatic ducts. Occasionally, the flukes migrate into the gallbladder and the pancreatic ducts. Adult flukes, which can live for more than twenty years, are 10 to 25 millimeters (mm) long and 3 to 5 mm wide.
Risk Factors
The greatest risk factor for contracting clonorchiasis is eating uncooked or undercooked fresh-water fish or crayfish imported from the Far East. Fish from this region should be thoroughly cooked to avoid the liver fluke infection. Clonorchiasis is in turn a known risk factor for the development of cholangiocarcinoma, a neoplasm of the biliary duct system.
Symptoms
Minor liver fluke infections are typically asymptomatic. Higher-level infections can cause fever, chills, abdominal pain, nausea, diarrhea, mild jaundice, and eosinophilia. Bilirubin levels may be elevated. Severe fluke infestation may cause stenosis of the bile ducts and develop into cholangiohepatitis and liver failure. In long-standing infections, cholangitis, cholelithiasis, pancreatitis, and cholangiocarcinoma can develop.
Screening and Diagnosis
A medical history should include questions about the person’s diet, travel history, and history of regions where the patient has lived. A physical examination should include gentle palpation of the liver. Medical tests often include endoscopy and an examination of stool.
Diagnosis of clonorchiasis typically depends on recovering and identifying the liver fluke’s eggs in a stool sample. Abdominal X-rays, computed tomography (CT) scans, and sonographic assessments may be used to identify diffuse dilatation of small intrahepatic ducts or thickening of the bile duct walls. The adult fluke may also be recovered surgically.
Treatment and Therapy
The drugs of choice for treating clonorchiasis are praziquantel or albendazole. Praziquantel paralyzes the musculature of the fluke, leading to its death. Albendazole inhibits metabolism in the cells of the fluke, causing immobilization and death; eradication of the fluke should be confirmed one month after treatment. In most cases, a single course of either drug is necessary, but for severe infections, longer-term treatment may be required.
Prevention and Outcomes
The best way to avoid clonorchiasis is to refrain from eating fish imported from the Far East. If eaten, however, the fish should be thoroughly cooked.
Bibliography
Berger, Stephen A., and John S. Marr. Human Parasitic Diseases Sourcebook. Sudbury, Mass.: Jones and Bartlett, 2005.
“Clonorchis FAQs.” Centers for Disease Control and Prevention, US Department of Health and Human Services, 25 Nov. 2014, www.cdc.gov/parasites/clonorchis/faqs.html. Accessed 25 Oct. 2017.
Icon Health. The Official Patient’s Sourcebook on Clonorchiasis. San Diego, Calif.: Author, 2002.
“Intestinal Trematodes” In Diagnostic Medical Parasitology, edited by Lynne Shore Garcia. 5th ed. Washington, D.C.: ASM Press, 2007.
Kaplan, Roberta R., and Tanja Schub. “Clonorchiasis.” CINAHL Nursing Guide, EBSCO Publishing, 16 Sept. 2016. Nursing Reference Center Plus, search.ebscohost.com/login.aspx?direct=true&db=nup&AN=T702612&site=eds-live. Accessed 25 Oct. 2017.
“Liver and Lung Trematodes.” In Diagnostic Medical Parasitology, edited by Lynne Shore Garcia. 5th ed. Washington, D.C.: ASM Press, 2007.
Sithithaworn, Paiboon, et al. “Food-Borne Trematodes.” In Manson’s Tropical Diseases, edited by Gordon C. Cook and Alimuddin I. Zumla. 22d ed. Philadelphia: Saunders/Elsevier, 2009.