How is an Ascaris infection spread?
Ascaris eggs are found in human feces. After feces contaminate the soil, the eggs become infectious after a few weeks. Infection occurs when a person accidentally ingests (swallows) infectious Ascaris eggs. Once in the small intestines, immature worms hatch from the eggs. The larvae are carried through the lungs and then to the throat where they are swallowed. Once swallowed, they reach the intestines and develop into adult worms. Adult female worms lay eggs that are then passed in feces; this cycle will take between 2-3 months. Pigs can be infected with another species of Ascaris. Occasionally, a pig Ascaris infection can be spread to humans; this occurs when infective eggs, found in the soil and manure, are ingested. Infection is more likely if pig feces are used as fertilizer in the garden; crops then become contaminated with Ascaris eggs.
