Unembryonated eggs are passed in the sputum of a human or feline. Two weeks later, miracidia develop in the egg and hatches. The miracidia penetrate its first intermediate host (snail). Within the snail mother sporocyst form and produce many mother rediae, which subsequently produce many daughter rediae which shed crawling cercariae into fresh water. The crawling cercariae penetrate fresh water crabs and encyst in its muscles becoming metacercaria. Humans or felines then eat the infected crabs raw. Once eaten, the metacercaria excysts and penetrates the gut, diaphragm and lung where it becomes an adult worm in pairs.