Download E. Pathology and Symptoms

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