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While usually found in the lung, the roundworm larva slip into the body through another route, the mucous membrane of the eye being a common example. If this occurs, then the larva must find their way to the gut.

This is something of a challenge for the larva, who are specialized for survival in the intestine, not in other parts of the body.

However, they do migrate through the body, snce they must find their way to the digestive system or starve to death.

Often their route goes through the lung. The lung is an especially sensitive organ when it comes to foreign bodies and quickly forms cysts aroung the offending worms. The worms, unable to go farther, stay where they are, and the cyst grows ever bigger, cancer like. This condition is known ad larva migrans and can be quite harmful.