Angiostrongylus cantonensis Life Cycle

1. Adult nematodes (worms) of A. cantonensis live in the pulmonary arteries of rats. Females lay eggs that hatch into larvae (first-stage).

2. First-stage larvae migrate to the pharynx, are swallowed, and are passed in the feces.

3. First-stage larvae penetrate or are ingested by an intermediate host (snail or slug) and develop into third-stage larvae.

4. When an intermediate host is ingested by the definitive host, the third-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.

5. Humans can acquire the infection by eating raw or undercooked infected snails or slugs, raw produce that contains a small snail or slug or part of one, or a transport host such as certain land crabs, frogs, toads, or freshwater prawns or shrimp.

6. In humans, the larvae migrate from the gastrointestinal tract to the meninges. Occasionally, they invade the eyes or lungs. A. cantonensis do not reach full maturity in humans.