Trichuris trichiura

Whipworm
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Adenophorea
Order:	Trichocephalida
Family:	Trichuridae
Genus:	Trichuris
Species:	T. trichiura
Binomial name
Trichuris trichiura (Linnaeus, 1771)

The round worm (Trichuris trichiura or Trichocephalus trichiuris) is a worm that causes trichuriasis when it infects a human large intestine. It is commonly known as the whipworm which refers to the shape of the worm; it looks like a whip with wider "handles" at the posterior end.

Life cycle

The female T. trichiura produces 2,000–10,000 single-celled eggs per day.^[1] Eggs are deposited from human feces to soil where, after two to three weeks, they become embryonated and enter the “infective” stage. These embryonated infective eggs are ingested and hatch in the human small intestine exploiting the intestinal microflora as hatching stimulus.^[2] This is the location of growth and molting. The infective larvae penetrate the villi and continue to develop in the small intestine. The young worms move to the cecum and penetrate the mucosa and there they complete development to adult worms in the large intestine. The life cycle from time of ingestion of eggs to development of mature worms takes approximately three months. During this time, there may be limited signs of infection in stool samples due to lack of egg production and shedding. The female T. trichiura begin to lay eggs after three months of maturity. Worms can live up to five years, during which time females can lay up to 20,000 eggs per day.

Recent studies using genome-wide scan revealed two quantitative trait loci on chromosome 9 and chromosome 18 may be responsible for genetic predisposition or susceptibility to infection of T. trichiura by some individuals.

Morphology

Trichuris trichiura has a narrow anterior esophageal end and shorter and thicker posterior anus. These pinkish-white worms are threaded through the mucosa. They attach to the host through their slender anterior end and feed on tissue secretions instead of blood. Females are larger than males; approximately 35–50 mm long compared to 30–45 mm.^[3] The females have a bluntly round posterior end compared to their male counterparts with a coiled posterior end. Their characteristic eggs are barrel-shaped and brown, and have bipolar protuberances.

Epidemiology

There is a worldwide distribution of Trichuris trichiura, with an estimated 1 billion human infections.^[4][5][6] However, it is chiefly tropical, especially in Asia and, to a lesser degree, in Africa and South America. Within the United States, infection is rare overall but may be common in the rural Southeast, where 2.2 million people are thought to be infected. Poor hygiene is associated with trichuriasis as well as the consumption of shaded moist soil, or food that may have been fecally contaminated. Children are especially vulnerable to infection due to their high exposure risk. Eggs are infective about 2–3 weeks after they are deposited in the soil under proper conditions of warmth and moisture, hence its tropical distribution.

Infection

Infection occurs through ingestion of eggs (which are usually found in dry goods such as beans, rice, and various grains) and is more common in warmer areas. The eggs hatch in the small intestine, and then move into the wall of the small intestine and develop. On reaching adulthood, the thinner end (the front of the worm) burrows into the large intestine and the thicker end hangs into the lumen and mates with nearby worms. The females can grow to 50 mm (2 inches) long. Neither the male nor the female has much of a visible tail past the anus.^[1]

Whipworm commonly infects patients also infected with Giardia, Entamoeba histolytica, Ascaris lumbricoides, and hookworms.

Symptoms and pathology

• Light infestations (<100 worms) are frequently asymptomatic.
• Heavy infestations may have bloody diarrhea.
• Long-standing blood loss may lead to iron-deficiency anemia.
• Rectal prolapse is possible in severe cases.
• Vitamin A deficiency may also result due to infection.^[3]

Mechanical damage to the mucosa may occur as well as toxic or inflammatory damage to the intestines of the host.

Diagnosis

Trichuriasis can be diagnosed when T. trichiura eggs are detected in stool examination. Eggs will appear barrel-shaped and unembryonated, having bipolar plugs and a smooth shell.^[6] Rectal prolapse can be diagnosed easily using defecating proctogram and is one of many methods for imaging the parasitic infection. Sigmoidoscopy show characteristic white bodies of adult hanging from inflamed mucosa (coconut cake rectum).

Treatment and control

Mebendazole is 90% effective in the first dose, and albendazole may also be offered as an anti-parasitic agent. Adding iron to the bloodstream helps solve the iron deficiency and rectal prolapse. Difetarsone is also an effective treatment.

Infection can be avoided by proper disposal of human feces, avoiding fecal contamination of food, not eating dirt, and avoiding crops fertilized with night soil. Simple and effective proper hygiene such as washing hands and food is recommended for control.

Vaccine Research

Development of subunit vaccines requires the identification of protective antigens and their formulation in a suitable adjuvant. Trichuris muris is an antigenically similar laboratory model for T. trichiura. Subcutaneous vaccination with adult excretory–secretory products (ES) protects susceptible mouse strains from T. muris. Larval stages may contain novel and more relevant antigens which when incorporated in a vaccine induce worm expulsion earlier in infection than the adult worm products. Nematode vaccines marketed to date have been of the irradiated larval type and used exclusively for the treatment of animals. These vaccines are not stable and require annual production, involving the yearly production and sacrifice of donor animals for passage. There has been much interest in the production of subunit vaccines against human and agricultural parasites since the early 1980s. Development of subunit vaccines requires the identification of protective antigens and their formulation with a suitable adjuvant to stimulate the immune response appropriately.

Dog and cat whipworms

Egg of Trichuris vulpis

Egg of Trichuris trichura

Whipworms develop when a dog swallows whipworm eggs, passed from an infected dog. Symptoms may include diarrhea, anemia, and dehydration. The dog whipworm (Trichuris vulpis) is commonly found in the U.S. It is hard to detect at times, because the numbers of eggs shed are low, and they are shed in waves. Centrifugation is the preferred method. There are several preventives available by prescription from a veterinarian to prevent dogs from getting whipworm.

The cat whipworm is a rare parasite. In Europe, it is represented mostly by Trichuris campanula, and in North America it is Trichuris serrata more often.^[7][8] Whipworm eggs found in cats in North America must be differentiated from lungworms, and from mouse whipworm eggs just passing through.

Whipworm as a therapeutic agent for IBD and other inflammatory disorders

The hygiene hypothesis suggests that various immunological disorders that have been observed in humans only within the last 100 years, such as Crohn's disease, or that have become more common during that period as hygienic practices have become more widespread, may result from a lack of exposure to parasitic worms (also called helminths) during childhood. The use of Trichuris suis ova (TSO, or pig whipworm eggs) by Weinstock, et al., as a therapy for treating Crohn's disease^[9][10][11] and to a lesser extent ulcerative colitis^[12] are two examples that support this hypothesis. There is also anecdotal evidence that treatment of inflammatory bowel disease (IBD) with TSO decreases the incidence of asthma,^[13] allergy,^[14] and other inflammatory disorders.^{[citation needed]} Some scientific evidence suggests that the course of multiple sclerosis may be very favorably altered by helminth infection;^[15] TSO is being studied as a treatment for this disease.^[16][17] Recent clinical results of TSO on Crohn's disease terminated with no improvement over placebo results.^[18]

See also

• Helminthic therapy
• Human parasitic diseases
• List of parasites (human)
• Worm
• Ötzi

References

• "Trichuris Trichiura: eMedicine Emergency Medicine". Emedicine.medscape.com. 2009-05-05. Retrieved 2009-05-19. 

1. ↑ 1.0 1.1 Books. "Trichuris Trichura". Ncbi.nlm.nih.gov. Retrieved 2009-05-19. 
2. ↑ K. S. Hayes et al.; Explotation of the Intestinal Microflora by Parasitic Nematode Trichuris muris; Science (2010); 328,1391
3. ↑ 3.0 3.1 "Trichuris trichiura definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms". Medterms.com. 2000-04-15. Retrieved 2009-05-19. 
4. ↑ DW Compton. How much human helminthiasis is there in the world? J Parasitol. 85, 397-403 (1999).
5. ↑ NR deSilva, S Booker, PJ Hotez, A Montresor, D Engles, L Savioli. Soil-Transmitted helminth infections: Updating the Global Picture. Trends Parasitol. 19, 547-551 (2003).
6. ↑ 6.0 6.1 "Trichuris trichiura". WrongDiagnosis.com. 2009-05-06. Retrieved 2009-05-19. 
7. ↑ "Whipworms". VeterinaryPartner.com. 24 September 2007. Retrieved 2009-05-19. 
8. ↑ Hendrix CM, Blagburn BL, Lindsay DS (1987). "Whipworms and intestinal threadworms". Vet. Clin. North Am. Small Anim. Pract. 17 (6): 1355–75. PMID 3328393. 
9. ↑ Hunter MM, McKay DM (2004). "Review article: helminths as therapeutic agents for inflammatory bowel disease". Aliment. Pharmacol. Ther. 19 (2): 167–77. doi:10.1111/j.0269-2813.2004.01803.x. PMID 14723608. 
10. ↑ Summers RW, Elliott DE, Urban JF, Thompson R, Weinstock JV (2005). "Trichuris suis therapy in Crohn's disease". Gut 54 (1): 87–90. doi:10.1136/gut.2004.041749. PMC 1774382. PMID 15591509. 
11. ↑ Summers RW, Elliott DE, Qadir K, Urban JF, Thompson R, Weinstock JV (2003). "Trichuris suis seems to be safe and possibly effective in the treatment of inflammatory bowel disease". Am. J. Gastroenterol. 98 (9): 2034–41. doi:10.1111/j.1572-0241.2003.07660.x. PMID 14499784. 
12. ↑ Buning, J; et al. (march 2008). "Helminths as governors of inflammatory bowel disease". Gut 57 (8): 1182–1183. doi:10.1136/gut.2008.152355. PMID 18628388. Retrieved 2010-12-10. "in our patient Treg [regulatory T cells] activated by helminthosis [T. suis infestation] were most likely the key element protecting a host with latent ulcerative colitis against development of a severe protcocolitis. (1183)"  Cite uses deprecated parameters (help)
13. ↑ "Helminthic Therapy: How to put your Asthma, Colitis, IBD, Crohn's or Multiple Sclerosis into remission with hookworm". Asthmahookworm.com. Retrieved 2009-05-19. 
14. ↑ "Allergies: Trichuris suis Ova (TSO) Therapy to Treat Food Allergies". Allergizer.com. Retrieved 2009-05-19. 
15. ↑ Correale J, Farez M. (2007). "Association between parasite infection and immune responses in multiple sclerosis". Annals of Neurology 61 (2): 97–108. doi:10.1002/ana.21067. PMID 17230481. 
16. ↑ "Asphelia Announces Initiation of an Independent TSO Trial for Multiple Sclerosis". redOrbit. 2008-04-07. Retrieved 2009-05-19. 
17. ↑ "Trichuris suis-induced modulation of human dendritic cell function is glycan-mediated". International journal for parasitology. 2012-12-06. Retrieved 2013-01-05. 
18. ↑ "CORONADO BIOSCIENCES ANNOUNCES TOP-LINE RESULTS FROM ITS TRUST-I PHASE 2 CLINICAL TRIAL OF TSO FOR THE TREATMENT OF CROHN’S DISEASE". 2013-10-14. 

External links

Wikimedia Commons has media related to Trichuris trichiura.

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