John S. Schieffelin and Richard A. Oberhelman
Trichuriasis is caused by infection of the large intestine with Trichuris trichiura, the whip-worm. Whipworm infection is cosmopolitan, but it is far more common in warm, moist climates, where the distribution of Trichuris and Ascaris overlap.1,2 Approximately 604 million people are infected worldwide. Infection is generally acquired in childhood; whipworm ova often pollute the ground where children play. Transmission of infection occurs by ingesting embryonated eggs, which may contaminate hands or food, including fruits and vegetables, that were fertilized using human feces.3 The life-cycle is shown in eFig. 333.1 .
T trichiura is a distinctive nematode with a thin, whiplike anterior and a broader posterior portion. Males are 3.0 to 4.5 cm long, with a coiled posterior end; females are 3.5 to 5.0 cm long, with a blunt posterior end. The eggs are barrel-shaped, 50 μm by 22 μm, usually yellowish-brown with translucent polar plugs (Fig. 333-1). Adult worms live in the cecum with their anterior portions anchored in the mucosa. The appendix and the lower ileum may also be infected. The female lays 3000 to 10,000 eggs daily, which pass out in feces. An infective-stage larva develops within the egg after 3 weeks in warm, shady, moist soil. After ingestion, the larvae hatch in the duodenum and migrate to the cecum, where they develop into mature, egg-laying adults within 1 to 3 months.
FIGURE 333-1. Egg of Trichuris trichiura. (Source: http://www.dpd.cdc.gov/dpdx/HTML/Ascariasis.htm. Accessed January 13, 2008.)
The whipworm produces an inflammatory focus at the mucosal attachment site and ingests whole blood. Heavy infections may be associated with superficial mucosal erosions, colitis, and in young children, rectal prolapse. Heavily infected persons may develop anemia of chronic disease, primarily thought to be due to inflammation in the large intestine. Hookworm infection often coexists with whipworm infection and may contribute to anemia. Eosinophilia of up to 25% can be found, but is rare.
CLINICAL MANIFESTATIONS, DIAGNOSIS, AND TREATMENT
Light infections are usually asymptomatic. Occasionally, there may be anorexia or vague abdominal discomfort. In moderate infections, abdominal pain (often in the right lower quadrant), low-grade fever, nausea, vomiting, weight loss, and pruritus are the most frequent complaints. Heavy infections may be accompanied by diarrhea, tenesmus, blood-streaked stools, and rectal prolapse, often with worms visibly imbedded in the rectal mucosa. Trichuriasis is difficult to differentiate clinically from other intestinal nematode infections or from intestinal amebiasis. Chronic infection can lead to impaired growth, physical fitness, and cognitive function.
Diagnosis is made by examining the stool for the characteristic ova. Concentration techniques may increase the yield in light infections. Mebendazole (Vermox) is commonly used for treating trichuriasis in both adults and children.4,5 The dose is the same for adults and children (100 mg by mouth twice daily for 3 days or 500 mg once), although single-dose mebendazole therapy for trichuriasis is not reliably effective. Albendazole is an excellent alternative, and according to some studies is significantly better than mebendazole. The dose is 400 mg daily for 3 days. Studies of mass chemotherapy have found that 800 mg once is equally if not more effective in decreasing the prevalence of trichuriasis.6 Problems with rectal prolapse subside with treatment.