Ascariasis

Definition:

An infection caused by a parasitic roundworm, Ascaris lumbricoides.

Causes, incidence, and risk factors:

This is the most common intestinal worm infection. It is found in association with poor personal hygiene, poor sanitation, or where human feces are used as fertilizer. Infection occurs when food or drink contaminated with roundworm eggs is ingested. The eggs hatch releasing larvae within the intestine. The larvae then migrate through the blood stream to the lungs, exit through the bronchial tree and are swallowed. (During migration through the lungs the larvae may produce an eosinophilic pneumonia.) Once back in the gut they mature into adult roundworms. Adult worms live in the intestine where they lay eggs that are expelled with the feces.

It is estimated that 1 billion people are infected worldwide. The infection occurs in all ages, though children seem to be affected more severely than adults.