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Trichuriasis (Trichuris trichiura)
Etiology
Trichuriasis is caused by the whipworm , Trichuris trichiura, a nematode, or roundworm, that inhabits the cecum and ascending colon. The principal hosts of T. trichiura are humans, who acquire infection by ingesting embryonated, barrel-shaped eggs ( Fig. 319.1 ). The larvae escape from the shell in the upper small intestine and penetrate the intestinal villi. The worms slowly move toward the cecum, where the anterior three-quarters whiplike portion remains within the superficial mucosa and the short posterior end is free in the lumen ( Fig. 319.2 ). In 1-3 mo, the adult female worm begins producing 5,000-20,000 eggs per day. After excretion in the feces, embryonic development occurs in 2-4 wk with optimal temperature and soil conditions. The adult worm life span is approximately 2 yr.
Epidemiology
Trichuriasis occurs throughout the world and is especially common in poor rural communities with inadequate sanitary facilities and soil contaminated with human or animal feces. Trichuriasis is one of the most prevalent human helminthiases, with an estimated 1 billion infected individuals worldwide. In many parts of the world, where protein-energy malnutrition and anemia are common, the prevalence of T. trichiura infection can be as high as 95%. Although trichuriasis occurs in the rural southeastern United States, its prevalence has not been reported. The highest rate of infection occurs among children 5-15 yr old. Infection develops after ingesting embryonated ova by direct contamination of hands, food (raw fruits and vegetables fertilized with human feces), or drink ( Fig. 319.3 ). Transmission can also occur indirectly through flies or other insects.
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