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Clonorchis sinensis A-Classification Phylum: Platyhelminthes (flatworms) Class: Trematoda (flukes) Family: Opisthorchiidae Genus/Species: Clonorchis sinensis (Chinese Liver Fluke) B. Morphology Clonorchis sinensis are “the most important flatworms” to humans. They don’t actually live in the liver. They live in the bile duct in the liver. These worms have a life span of 8 years. They can infect vertebrates such as cat, dogs, pigs and humans. The size of C. sinensis is 1-2 centimeters (0.5-1 in) and ~4 mm (~0.4 in) wide. The fluke makes 4000 watermelon shaped eggs daily. The eggs are 25 µm in length. They are often confused with the eggs of Opisthorchis felinius, which are 11-12 µm narrower. The egg has an operculum and a small knob on the posterior end, which makes Somewhat unique. The fluke is narrow at the anterior end and rounded at the posterior. C. Lifecycle and Epidemiology Snails eat the eggs in fresh waters. The most common suitable snail is Parafossarulus manchouricus that C.sinensis can use as an intermediate host. In the snail it goes through a series of development stages. The egg become a miracidia which then form sporocysts that eventually will make rediae that will be come free swimming cercariae. The cercariae have eyespots so can sense dark and light and can sense motion. The cercariae will eventually bore under the scale or into the muscle of a fish of the family Cyprinidae (100 species incl. carp and goldfish) and form a cyst called metacercariae. The cyst is the infectious stage of the parasite. If a vertibrate animal (definitive host) eats uncooked, salted, pickled or smoked infected fish the metcercariae will excyst in the duodenum and the juvenile worm will travel to the biliary ducts. It takes 1 month for it to fully develop. 1 D-Geographic Distribution The Chinese Live Fluke is found primarily in Asia, including China, Taiwan, Korea, Vietnam, and Japan. 2 E. Pathology and Symptoms Many cases of Clonorchis sinensis are asymptomatic when there is a light infection. When a person is initially infected with a large number of metacercariae, they will show acute symptoms of infection. These symptoms include fatigue, fever, joint pain, an enlarged liver, abdominal pain, occasional jaundice, eosinophilia and at times leukocytosis. After about a month these symptoms will lessen, and eggs will be present in the person’s feces. Stenosis, the constriction or narrowing, of the bile duct can occur if there had been reoccurring infections in the host. Liver dysfunction can also occur in patients with reoccurring infection. The average Clonorchiasis infection is between 20 to 200 worms but as many as 21,000 have been found in a single host. It affects approximately 20 million people worldwide. Section of Clonorchis sinensis in the bile duct. Note the thickening of the bile duct walls (*). F. Diagnosis Diagnosis can be done by identifying the eggs from a stool sample or from aspirates taken from the duodenum. It takes about a month after first contracting the infection to find eggs in the stool. The actual adult worms are only seen when surgery or an autopsy is performed. Heterophyles heterophyles eggs are identical in structure. Stool sample containing Clonorchis sinensis eggs. 3 G. Treatment This infection is treated with the drug praziquantel. This drug increases the permeability of the worm’s cell membranes. This causes the amount of Ca++ ions to increase in the muscle cells, which makes them contract. The drug also causes vacuolization and deterioration of the outer surface of the worm. 25mg/kg of praziquantel should be administered three times a day for two days to be effective. H-Public Health Strategies/Eradication People are infected primarily through eating infected fish that are not thoroughly cooked. Therefore, the most effective method for eradication of Clonorchis sinensis infections is to fully cook all fish products before ingestion. However, this is a difficult method to implement as eating raw fish is a large part of Asian culture. Raw fish is considered a delicacy in many parts of Asia and the ability to afford it is a sign of affluence. A possible way around this would be to freeze the fish prior to ingestion as this is an effective method for killing some Trematodes. However, the Clonorchis sinensis are metacercariae are so resistant to freezing that even 7 days spent at -20 degrees Celsius has no effect on them. Another significant problem in the eradication of Clonorchis sinensis is that many people do not have access to a reliable detection method such as a fecal screening. In addition, it is common practice for human feces to be used as fertilizer for crops. Therefore, human waste is not generally exposed to sewage treatment, and many areas cannot afford a sewage system anyway. The best way to eradicate Clonorchis sinensis from a given area would be to change the cultural habits to prevent the ingestion of uncooked fish through health education. In addition, the development of good hygiene habits and a sewage treatment system would be very beneficial. Another advantageous strategy would be to control the snail populations within the area. 4 Works cited Carlo Denegri Foundation. Aug 2004. < http://www.cdfound.to.it/html/clo1.htm > Accessed Jan 23, 2005 Eckroad, E. and H. Lee. 2001. "Clonorchis sinensis" (On-line), Animal Diversity Web. <http://animaldiversity.ummz.umich.edu/site/accounts/information/Clonorchis_sinensis.html. >Accessed January 23, 2005 Graphic Images of Parasites. < http://www.biosci.ohio-state.edu/~parasite/clonorchis.html > Accessed Jan 23, 2005 Hiong, Chi U. Go. March 19, 2003. e-Medicine Intestinal Flukes. < http://www.emedicine.com/med/topic1177.htm> Accessed Jan 22, 2005. Houseman, Antoine Morin Jon.BIODIDAC. <http://biodidac.bio.uottawa.ca/Thumbnails/searchresults.htm > Accessed Jan 23, 2005. Johnson, Raven. Biology. 3ed. McGraw-Hill higher Education. NYC. 2002 Dr. Joseph F. Smith Medical Library, May7, 2004. Fluke infections < http://www.chclibrary.org/micromed/00048520.html#Treatment> Accessed Jan 22, 2005. Schmidt, D.Gerald & Roberts, Larry S. Foundation of Parasitology. 8th ed. USA. 2000. Zeibig, Elizabeth A. Clinical parasitology: A Practical Approach. W.B Saunders Company. USA. 1997 Markell and Voger. Medical parasitoloy. 8th ed. WB Saunders Company 1999 Bareza Rasoul Sasha McClain Kay Magnuson 25 January 2005 5