Biology - Life Cycle of Capillaria philippinensis
Typically, unembryonated eggs are passed in the human stool and become embryonated in the external environment ; after ingestion by freshwater fish, larvae hatch, penetrate the intestine, and migrate to the tissues . Ingestion of raw or undercooked fish results in infection of the human host . The adults of Capillaria philippinensis (males: 2.3 to 3.2 mm; females: 2.5 to 4.3 mm) reside in the human small intestine, where they burrow in the mucosa . The females deposit unembryonated eggs. Some of these become embryonated in the intestine, and release larvae that can cause autoinfection. This leads to hyperinfection (a massive number of adult worms) . Capillaria philippinesis is currently considered a parasite of fish eating birds, which seem to be the natural definitive host .
Life cycle image and information courtesy of DPDx.