Adult worms of A. cantonensis live in the pulmonary arteries of rats. Females lay eggs that hatch into larvae (first-stage). First-stage larvae migrate to the pharynx, are swallowed, and are passed in the feces. First-stage larvae penetrate or are ingested by an intermediate host (snail or slug) and develop into 3rd-stage larvae. When an intermediate host is ingested by the definitive host, the 3rd-stage larvae migrate to the brain, where they develop into young adults. The young adults return to the venous system and then to the pulmonary arteries, where they mature. Humans can acquire the infection by eating raw or undercooked infected snails or slugs or by eating raw produce that contains a small snail or slug or part of one.
Image from the Centers for Disease Control and Prevention Image Library.