Capillaria philippinensis causes human intestinal capillariasis. Two other Capillaria species parasitize animals, with rare reported instances of human infections. They are C. hepatica , which causes in humans hepatic capillariasis, and C. aerophila , which causes in humans pulmonary capillariasis. Ingestion of raw or undercooked fish results in infection of the human host.
Humans are the only demonstrated hosts .
The females deposit unembryonated eggs. Some of these embryonate in the intestine, and release larvae that can cause autoinfection. Capillaria philippinesis is currently considered a parasite of fish eating birds, which seem to be the natural definitive host . Capillaria hepatica adult worms reside in the liver of various animals, especially rats. The females produce eggs that are retained in the liver parenchyma.