Excerpt from Trichuris Trichiura

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Background

Trichuris trichiura, or the whipworm, is notable for its small size compared with Ascaris lumbricoides. Around the world, trichuriasis is a very common intestinal helminthic infection, and about one quarter of the world 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. Only patients with heavy infections become symptomatic. Poor hygiene is associated with trichuriasis transmission, and children are especially vulnerable because of their high exposure risk.

The worm 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 eosinophilia. The cecum and colon are the most commonly infected sites.

Note that T trichiura is usually found in association with other helminths that flourish under similar conditions, a common pathogen being A lumbricoides.

Pathophysiology

After 10-14 days in soil, eggs become infective. Trichuriasis is transmitted by the fecal-oral route, as with A lumbricoides, but in contrast to this parasite and to hookworm, no tissue migratory phase occurs. 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. Adult females lay eggs for up to 5 years.

Immunologically, cytokines such as interleukin 25 (IL-25) mediate type 2 immunity and are required for the regulation of inflammation in the gastrointestinal tract.

Frequency

United States

Whipworm infection is rare overall but is less rare in the rural Southeast, where 2.2 million people are infected.

International

Whipworm infection is common in less-developed countries. This parasite is carried by nearly one quarter of the world population.

Mortality/Morbidity

Whipworm infection is rarely fatal. 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, due to a higher propensity to directly or indirectly consume soil, are more commonly and more heavily infected. Also, it is widely believed that partial protective immunity develops with age and children are not protected initially.

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