Trichuris trichiura
A. Classification
Phylum: Nematoda
Family: Trichuridae
Genus species: Trichuris trichiura
Common name “human whipworm”
B. Morphology
The adult nematode looks like a whip and is generally 3 to 5 cm long, with the males being
somewhat smaller than the females. The anterior three-fifths of the worm is mostly threadlike,
while the posterior two-fifths is fatter and contains reproductive organs. The esophagus occupies
about two-thirds the body length and is surrounded by stitchocytes. Stitchocytes are large,
unicellular glands. The mouth lacks lips and has a simple opening. The buccal cavity is tiny.
The anus is located near the tip of the tail. The male has a curved tail and has a single spicule
that is surrounded by a spiny spicule sheath. The female’s vulva is near the junction of the
esophagus and the intestine. Both sexes have a single gonad.
The eggs are approximately 50 to 54μm by 22 to 23μm. Trichuris trichiura eggs are barrel
shaped with two terminal polar plugs. The external layer of the shell of the egg is smooth and
generally yellow-brown in color.
Figure 1: The female and male adults.
Figure 2 (Far Left):
Posterior part of male
Figure 3 (Left):
Posterior part of female
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Figure 4: Trichuris trichiura egg
C. Life Cycle
Figure 5. Lifecycle of Trichuris trichiura
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The adult worms are approximately 4 cm in length and live in the cecum and ascending colon.
The adult worms are fixed in that location, with the anterior portions threaded into the mucosa.
The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed
between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year.
The eggs exit with the feces and in the soil can develop into a 2-cell stage. They then develop
into an advanced cleavage stage from which they embryonate. Eggs become infective in 15 to
30 days. After ingestion from soil-contaminated hands or food, the eggs hatch in the small
intestine, and release larvae. Larvae mature and establish themselves as adults in the colon
without undergoing the venous pulmonary migration. The worm takes about three months to
fully develop and become sexually mature.
D. Geographic Distribution
Human whipworm infections occur worldwide, but predominantly in tropical climates. It is most
prevalent in areas with poor sewage disposal. In the US it occurs primarily in the southern
states. More than 500 million people are infected worldwide. About 2.2 million people are
infected in southeastern United States, where 20 to 25% of the infections are in small children.
Figure 6: Areas in black represent the highest prevalence of Trichuris trichiura.
E. Pathology and symptoms
Trichuris trichiura infections are most frequently asymptomatic. It can cause growth retardation
and bloody diarrhea in heavy infections. Trauma to the intestinal epithelium and underlying
submucosa can cause a chronic hemorrhage that may result in anemia. Insomnia, nervousness,
loss of appetite, vomiting, prolonged diarrhea, constipation, and flatulence are some other
symptoms from heavy infections. Symptoms may be confused with those of hookworm.
amebiasis, or acute appendicitis. Death is a very rare occurrence.
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Figure 7: Trichuris trichiura adults with anterior end embedded in the intestinal mucosa of large
intestine.
F. Diagnosis
The eggs appear in the feces 70-90 days after ingestion of the parasite and are easy to see
because of their unique structure. It is advantageous to concentrate the ova for identification in
light infections. Identification of the adult worms by sigmoidoscopy is another method of
diagnosis.
G. Treatment of individual
Mebendazole is the drug that is used most often; albendazole is an alternative. One hundred mg
of Mebendazole should be taken twice a day for three days to get ride of the parasite. Training
of children and adults in sanitary disposal of feces and washing of hands is necessary to prevent
reinfection.
H. Public Health Strategies
Improved sanitation is the best possible method of eradication. Proper fecal disposal is
extremely important in the eradication of this parasite. It is very important that proper hand
washing is practiced along with properly washing all food to eliminate the possibility of fecaloral contact.
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Works Cited
Hong, Sung-Jong. “Trichuris trichiura.” Web Atlas of Medical Parasitology. 2003. Accessed
22 February 2005.
<http://www.atlas.or.kr/atlas/alphabet_view.php?my_codeName=Trichuris%20trichiura>
.
“Trichuriasis.” Centers for Disease Control and Prevention- Laboratory Identification of
Parasites of Public Health Concern. 13 Dec 2002. Accessed 22 February 2005.
<http://www.dpd.cdc.gov/DPDx/HTML/Trichuriasis.htm>.
“Trichuris spp.” Parasites and Parasitological Resources. Accessed 22 February 2005.
<http://www.biosci.ohio-state.edu/~parasite/trichuris.html>.
“Trichuris trichiura.” Intestinal Parasites. Accessed 22 February 2005.
<http://www.cdfound.to.it/html/tri1.htm#344>.
“Trichuris trichiura.” University of California, Davis- Department of Nematology. 1 February
2005. Accessed 22 February 2005.
<http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/nemas/trichuristrichiura>.
Weiss, Eric L. Trichuris trichiura. 13 July 2001. Accessed 22 February 2005.
<http://www.emedicine.com/emerg/topic842.htm>.
Michele Alfred
Angela Chung
Drew Dickinson
February 25, 2005
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