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Trichuris Trichiura
Updated: May 5, 2009
Introduction
Background
Globally, Trichuris trichiura, or whipworm, is a very common intestinal helminthic infection, and about one quarter of the world's population is thought to carry the parasite. Principally a problem in tropical Asia and, to a lesser degree, in Africa and South America, a lack of a tissue migration phase and a relative lack of symptoms characterize whipworm infection. Trichuris is also notable for its small size compared with Ascaris lumbricoides. Only patients with heavy parasite burden become symptomatic. Vitamin A deficiency has been seen in patients with T trichiura infection .
Poor hygiene is associated with trichuriasis transmission, and children are especially vulnerable because of their high exposure risk. This is especially true in developing countries, where poor sanitary conditions correlate with heavy disease burden and infections. One study in Nigeria was undertaken to determine helminth infection status and hygienic conditions in primary schools. Prevalence of helminth infection was higher in the schools where hygiene conditions (ie, tapwater, handwashing soap) were lacking. The study results recommended that the school health programs include deworming, health education, and improvement of hygiene conditions.1
The whipworm derives its name from its characteristic whiplike shape; the adult (male, 30-45 mm; female, 35-50 mm) buries its thin, threadlike anterior half into the intestinal mucosa and feeds on tissue secretions, not blood. This relative tissue invasion causes occasional peripheral eosinophilia. The cecum and colon are the most commonly infected sites, although in heavily infected individuals, infection can be present in more distal segments of the GI tract, such as the descending colon and rectum.
Adult males of Trichuris trichiura are 30-45 mm long, with a coiled posterior end. Adult females are 35-50 mm with a straight posterior end. Both sexes have a long, whip-like anterior end. Adults reside in the large intestine, cecum, and appendix of the host. Image shows the posterior end of an adult T trichiura, taken during a colonoscopy. Image courtesy of Duke University Medical Center and Centers for Disease Control and Prevention.
Note that T trichiura is usually found in association with other helminths that flourish under similar conditions, a common pathogen being A lumbricoides.
Pathophysiology
Trichuris, as with Ascaris lumbricoides, is spread via fecal-oral transmission. Eggs are deposited in soil through human feces. After 10-14 days in soil, eggs become infective. In contrast to other parasites, such as A lumbricoides, no tissue migratory phase occurs with Trichuris organisms, confining infection to the GI tract. Larvae hatch in the small intestine, where they grow and molt, finally taking up residence in the large intestine. The time from ingestion of eggs to development of mature worms is approximately 3 months. During this time, there may be no shedding of eggs and only limited evidence of infection in stool samples. Worms may live from 1-5 years, and adult female worms lay eggs for up to 5 years, shedding up to 20,000 eggs per day.
This is an illustration of the life cycle of Trichuris trichiura, the causal agent of trichuriasis. Image courtesy of Centers for Disease Control and Prevention, Alexander J. da Silva, PhD, and Melanie Moser.
Immunologically, cytokines such as interleukin 25 (IL-25) mediate type 2 immunity and are required for the regulation of inflammation in the gastrointestinal tract.
Recent linkage analyses of a genome-wide scan revealed that 2 quantitative trait loci on chromosomes 9 and 18 may be responsible for the susceptibility to infection with T trichiura in some genetically predisposed individuals.2
Frequency
United States
Whipworm infection is rare overall but is more common in the rural Southeast, where 2.2 million people are thought to be infected.
International
Whipworm infection is more common in less-developed countries. This parasite is carried by nearly one quarter of the world population.
Mortality/Morbidity
Whipworm infection is rarely fatal and is usually asymptomatic, but symptoms may be present in heavily infected individuals. Loose stools may be present with minimal blood with the development of chronic anemia if bleeding is chronic. Nocturnal stooling is quite common. Finger nail clubbing may also be present. In children, vitamin deficiencies (vitamin A) may contribute to developmental delay and growth retardation. Rectal prolapse may occur in heavily infected hosts.
Race
No racial predilection exists.
Sex
Boys are more likely to be infected because they are thought to eat more dirt than girls.
Age
Children are more commonly infected than adults due to poor hygiene and increased consumption of soil. Children are also more heavily infected. Furthermore, it is widely believed that partial protective immunity develops with age and children are not protected initially.
Clinical
History
Most patients are asymptomatic. Clinical symptoms are limited to patients with heavy infection, who tend to be small children or others with significant exposure. Note that there is no pulmonary migration and, thus, no pulmonary or extra-gastrointestinal symptoms.
- Nocturnal loose stools
- Dysentery can occur in patients with greater than 200 worms.
- Rectal prolapse
- Failure to thrive
- Symptoms of anemia (massive infection only)
- Vague abdominal discomfort
- Stunted growth
Physical
- Mild abdominal tenderness
- Signs of anemia
- Rectal prolapse
- Finger clubbing can sometimes suggest the diagnosis in infected patients.
- Direct visualization of adult worms on rectal mucosa via endoscopy or if rectum is prolapsed (adult worms only in lower colon in heavy infection)
Causes
Whipworm is caused by consumption of soil or food that has been fecally contaminated. (Eggs are infective or embryonated about 2-3 weeks after being deposited in the soil).
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| References |
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References
Ekpo UF, Odoemene SN, Mafiana CF, Sam-Wobo SO. Helminthiasis and hygiene conditions of schools in ikenne, ogun state, Nigeria. PLoS Negl Trop Dis. Jan 30 2008;2(1):e146. [Medline].
Williams-Blangero S, Vandeberg JL, Subedi J, Jha B, Dyer TD, Blangero J. Two quantitative trait loci influence whipworm (Trichuris trichiura) infection in a Nepalese population. J Infect Dis. Apr 15 2008;197(8):1198-203. [Medline].
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Drugs for Parasitic Infections. Medical Lett Drugs Ther; August 2004. [Full Text].
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Jackson TF, Epstein SR, Gouws E. A comparison of mebendazole and albendazole in treating children with Trichuris trichiura infection in Durban, South Africa. S Afr Med J. 1998;88(7):880-883. [Medline].
Jongsuksuntigul P, Jeradit C, Pornpattanakul S. A comparative study on the efficacy of albendazole and mebendazole in the treatment of ascariasis, hookworm infection and trichuriasis. Southeast Asian J Trop Med Public Health. Dec 1993;24(4):724-9. [Medline].
Kongsbak K, Wahed MA, Friis H, Thilsted SH. Acute-phase protein levels, diarrhoea, Trichuris trichiura and maternal education are predictors of serum retinol: a cross-sectional study of children in a Dhaka slum, Bangladesh. Br J Nutr. Oct 2006;96(4):725-34. [Medline].
Kringel H, Iburg T, Dawson H, et al. A time course study of immunological responses in Trichuris suis infected pigs demonstrates induction of a local type 2 response associated with worm burden. Int J Parasitol. Jul 2006;36(8):915-924. [Medline].
Uga S, Nagnaen W, Chongsuvivatwong V. Contamination of soil with parasite eggs and oocysts in southern Thailand. Southeast Asian J Trop Med Public Health. 1997;28 Suppl 3:14-7. [Medline].
Further Reading
Keywords
whipworm, trichuriasis, Trichuris trichiura, intestinal helminthic infection, whipworm infection
