Trichuris trichiura: A nematode (roundworm) also called the human whipworm. The third most common round worm of humans. Occurs worldwide, with infections more frequent in areas with tropical weather and poor sanitation practices, and among children. It is estimated that 800 million people are infected worldwide. Trichuriasis (infection with Trichuris trichiura) occurs in the southern United States.
The adult worms (approximately 4 cm in length) live in the cecum and ascending colon (the first part of the large intestine). Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The unembryonated eggs are passed with the stool. In the soil they embryonate and become infective in 15 to 30 days. After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae that mature and establish themselves as adults in the colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa (the lining) of the intestine. The females begin to oviposit (lay eggs) 60 to 70 days after infection. The life span of the adults is about 1 year.