This is the most common intestinal worm infection. It is found in association with poor personal hygiene, poor sanitation, and in places where human feces are used as fertilizer. Intake of food or drink contaminated with roundworm eggs causes infection.
The eggs hatch and release larvae within the intestine. The larvae then move through the bloodstream to the lungs, exit up through the large airways of the lungs, and are swallowed back into the stomach and intestines.
During movement through the lungs the larvae may produce an uncommon form of pneumonia called eosinophilic pneumonia. Once back in the intestines, they mature into adult roundworms. Adult worms live in the intestine where they lay eggs that are present in feces.
It is estimated that 1 billion people are infected worldwide. Ascariasis occurs in all ages, though children seem to be affected more severely than adults.
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