You will become infected if you eat vegetation that is contaminated with Ascaris eggs. Following ingestion, the immature worms will hatch in your small intestine and then undertake a bizarre migration through your circulatory system to your lungs, where they will be coughed up and then either spit out or swallowed. The swallowed worms will return to your small intestine via your digestive tract. The purpose of this migration is unknown, but several other species of hookworms behave in a similar manner.

Symptoms of infection include inflammation and hemorrhage of the liver and lungs due to an accumulation of dead larvae and tissue irritation. There have been documented cases where the worms have blocked the bile or pancreatic ducts, or penetrated the small intestine, leading to fatal complications.

Interestingly, these worms seem to react very negatively to anesthetics and will flee an anesthesized body. Numerous cases have been reported in which patients in surgical recovery rooms have had worms migrate from their small intestine, through their stomach, and out their nose or mouth.