Once you swallow contaminated food and drink, the eggs hatch and release immature roundworms called larvae within your intestine. The larvae move through the blood to the lungs, they then move up the lung through the large airways of the lungs and are swallowed back into the stomach and intestines. Once the larvae are back in the intestines they mature into adult roundworms that live there and lay eggs that are present in faeces.
Attribution: Avallain