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Trichuriasis

Trichuriasis is an infection of the human cecum, appendix, colon and rectum caused by the parasite, Trichuris trichiura. It is most commonly known as Whipworm Disease and is remembered in areas of high prevalence and poor socioeconomic and sanitary conditions.

Synonyms for Trichuriasis include: Whipworm infection, Trichocephaliasis, Trichocephalosis, Sp: Tricuriasis, Fr: Trichuriose, and Ger: Peitschenwurmbefall.

 

Trichuris trichiura

T. trichiura is a parasitic nematode (roundworm), from the Phylum Aschelminthes. It is often referred to as human whipworm.

Further taxonomy classification of whipworm includes:

Class: Adenophorea
Order: Stichosmida
Family: Trichocephaloidea


 

History

© Dr. Smith

The history of T. Trichuria dates back to the times of prehistoric man; however, the first written record of T. trchiura appeared in 1740 when an Italian scientist by the name of Morgani discovered the residence of adult T. trichiura worms in the colon. In 1761 Roedere, a German physician, gave a report of the exact morphologic description and provided accurate drawings of the parasite. The organism received its taxonomy classification in the 18th C.


 

Prevalence

© Tropical Medicine Resource Center.

 

Whipworm thrives best in warm, moist tropical countries. In some hyperendemic areas, 90% of the population is infected. Because of the fecal pollution, dense shade near the house, and heavy rainfall, the southern Appalachian Mountains and rural Louisiana have the highest incidence rates of the US.

1947 Country Estimates of T. trchiura Infections
Asia
227 million
Russia
27 million
Europe
34 million
Africa
28 million
tropical areas of the Americas
38 million

 

Other Estimates of Infection
Worldwide
WHO-1998
1 billion infected worldwide
1988
500 and 800 millionworldwide
United States
-
2 to 3 million
Brazil (large cities)
-
incidence upto 40%
Costa Rica
-

25% without diarrhea

50% with acute diarrhea

 

 

 


 

Epidemiology

The epidemiology of Trichuris is similar to that of Ascaris. The two parasites often cohabit in the same host. The whipworm is especially prevalent in areas of high rainfall, high humidity and dense shade.

One female Trichuris can produce 3,000-10,000 barrel-shaped ova daily. These are passed in the stool and measure 50 x 25 micra. In passing through the human intestine, bile impregnates the outer portion of the thick shell and cause the ova to gain a brownish color. The eggs require 2 to 4 weeks to develop into infective first stage larvae in warm damp soil under optimal conditions. Some eggs remain latent in the soil for 5 years and may remain infective for at least 1 to 2 years.

©  http://www.microscopyu.com/galleries/dicphasecontrast/trichurisdiclarge.html

Humans become infected by ingesting contaminated soil, food or water containing infective Trichuris eggs previously passed in feces. Small children aged 3 to 9 years are more often infected than adults. Because they are likely to play with contaminated soil, children develop heavy worm burdens from transferring embryonated eggs into their mouths with their fingers. In the United States and Europe, mentally handicapped children in institutions may have high rates of infection.

After ingestion, intestinal juices in the duodenum weaken the shell of the egg. The larva is then freed and attaches itself to the villi of the proximal small bowel for about a week. During this week, it gains nourishment until it continues into the cecum (its normal habitat) or elsewhere in the large intestine. After molting four times, the larva grows into the adult form and attaches to the mucosa.

In severe infections, Trichuris may infect the entire colon, including the rectum and appendix; it is rarely found in the terminal ileum. Once established, Trichuris may live in the bowel for several years, but because of its firm attachment to the intestinal mucosa the infection may be totally asymptomatic and undiscovered unless the patient also harbors other parasites, such as the freely moving Ascaris. If reinfection does not occur, most of the worms will die within 3 years.


 

Clinical Presentation

© Tropical Medicine Resource Center.

 

Patients usually discover that they are infected with T. trichuria when being inspected for the presence of other parasites. Most cases are asymptomatic and sometimes difficult to diagnose if only a few worms are present. T. trichuria is frequently found in combination with Ascaris, hookworm, or Entamoeba histolytica, which share a similar geographical distribution and have more severe symptoms.

Light infections with T. trichirua are usually asymptomatic.

Heavy infections are most frequently found in malnourished children.

Severe symptoms include:

In the severest of cases, severe chronic diarrhea or dysentery lasts 6 months to 3 years with blood and excess mucus in the stools, T. trichirua dysentery syndrome produces gastrointestinal problems, and chronic T trichuria colitis mimics other forms of inflammatory bowel disease and can result in growth retardation.

More minor symptoms include:

T. trichirua has also been associated with appendicitis in the tropics and allergic manifestations such as urticaria, rhinitis and eosinophilia are frequently seen.


 

Life Cycle

 

The unembryonated eggs are passed with the stool .  In the soil, the eggs develop into a 2-cell stage , an advanced cleavage stage , and then they embryonate ; eggs become infective in 15 to 30 days.  After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae that mature and establish themselves as adults in the colon .  The adult worms (approximately 4 cm in length) 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.


 

Morphology

© Tropical Medicine Resource Center.

 

Trichuris trichiura is typically 54 mm x 22 mm long, but sizes of the whipworm range from 49-65 mm x 20-29 mm. It is elongated, and barrel-shaped with a polar "plug" at each end. Its color varies from yellow to brown and the "plugs" are colorless. It appears as 1 cell or unsegmented in its stage of development when being passed.

© CDC DPDx – Trichuriasis

Specific features and variations of the T. trichiura include distinctive polar plugs and eggs which are occasionally oriented in a vertical or slanted position and not readily recognized. Gently tapping the coverslip will usually reorient the egg. Atypical eggs lacking polar plugs may be seen on rare occasions.

 

© http://www.biosci.ohio-state.edu/~parasite/trichuris.html

 

Female and male T. trichuria are easily distinguishable by the shape of their heads. The females have a straight and thick head while the mails have a curly ended head.

 

 

 

 


 

© google images

Transmission:

Reservoir:

Treatment Rx :

Public Health and Prevention Strategies:


 

Diagnostics

© Dr. Smith

 

Specific diagnosis is easily made in the laboratory or occasionally by air contrast barium enema, and is often confirmed by direct inspection of the rectum. The diagnosis depends on finding Trichuris eggs on stool concentration tests, or by identification of the adult worms, usually by sigmoidoscopy. Diagnostics for T.. trichirua include:


 

Useful Web Links:

CDC DPDx - Trichuriasis

Medical Dictionary Trichuriasis - WrongDiagnosis.com

Red Book On-line

Tropical Medicine Resource Center

Parasites and Pestilence: Infectious Public Health Challenges

International Task Force for Disease Eradication

Materials Safety Data Sheet, Canadian office of Laboratory Security

Center of Disease Control (CDC)

http://www.stanford.edu/class/humbio103/ParaSites2002/trichuriasis/Tirchhod.html

 

Contacts:

Dr. Scott Smith

 

References:

Astorgraphics, ScietificAmerican.com 2002

http://www.astrographics.com/cgi-bin/ase/ase.cgi?affiliate=sciam&mode=display&gallery=3&type=invertebrate&color=&keywords=&page=6

Coombs, Isabel, & Crompton, D.W.T. A Guide to Human Helminths London ; New York : Taylor and Francis, 1991.

CDC DPDx – Trichuriasis

http://www.dpd.cdc.gov/DPDx/HTML/Trichuriasis.asp?body=Frames/S-Z/Trichuriasis/body_Trichuriasis_page1.htm

Eric L Weiss, MD, DTM&H, Tirchuris trichiura, E-Medicine Journal, July 13 2001, Volume 2, Number 7. http://www.emedicine.com/emerg/topic842.htm

Freedman DO: Intestinal nematodes. In: Gorbach SL, Bartlett JG, Blacklow NR (eds) Infectious Diseases. Saunders, Philadelphia, 1992.

Ismail, M. M.; Jayakody, R. L. “Efficacy of albendazole and its combinations with ivermectin or diethlycarbamazine (DEC) in the treatment of Trichuris trichiura infections in Sri Lanka.” Annals of Tropical Medicine and Parisitology; July 1999; v93, no.5, p501-504.

Mahmoud A: Intestinal nematodes (roundworms). In: Mandell GL, Douglas RG Jr, Bennett (eds): Principles and Practice of Infectious Diseases, 3rd edn. Churchill Livingstone, New York, 1990

Markell, Edward K.; John, David T.; Krotoski, Wojciech A. Markell and Voge’s Medical Parisitology. Eight Ed. W.B. Saunders Co. New York, 1999.

Marty AM, Andersen EM: Helminthology. In: Doerr W, Seifert G (eds): Tropical Pathology, 2nd edn. Springer, Berlin Heidelberg New York, 1995, pp 871-875.Publication of CDC Surveillance Summaries. February 28, 1992 / 41(08);145-146.

http://www.cdc.gov/mmwr/preview/mmwrhtml/00016167.htm

http://www.dpd.cdc.gov/dpdx/HTML/Trichuriasis.htm

Medical Dictionary Trichuriasis - WrongDiagnosis.com

http://www.wrongdiagnosis.com/w/whipworm/stats.htm

Red Book On-line http://aapredbook.aappublications.org/cgi/content/full/2003/1/3.138#top

Reeder MM, Hamilton LC: Tropical diseases of the colon. Semin Roentgenol 3:62-80, 1968.

Strickland GT: Hunter's Tropical Medicine, 8th edn. Saunders, Philadelphia, 1998.

Tropical Medicine Resource Center. Chapter 17 Trichuriasis (Whipworm Infection), 2000.

http://tmcr.usuhs.mil/tmcr/chapter17/intro.htm

 

 

Website created by: Jessika Diaz

jkd@stanford.edu

May 2005