The nematode (roundworm) Capillaria philippinensis causes human intestinal capillariasis.
Typically,unembryonated eggs are passed in the human stool and become embryonated in the external environment ; after ingestion by freshwater fish, larvae hatch, penetrate theintestine, and migrate to the tissues . Ingestion of raw or undercooked fish results in infection of thehuman host. Humans are the only demonstrated hosts . The adults of Capillaria philippinensis (males: 2.3 to 3.2mm; females: 2.5 to 4.3 mm) reside in the human small intestine, where theyburrow in the mucosa . The females deposit unembryonated eggs. Some of thesebecome embryonated in the intestine, and release larvae that can causeautoinfection. This leads to hyperinfection (a massive number of adult worms) . Capillaria philippinesis is currently considered aparasite of fish eating birds, which seem to be the natural definitive host .
Capillaria philippinensis is endemic in the Philippines and also occurs in Thailand. Rare cases have been reported from other Asian countries, the Middle East, and Colombia.
Intestinal capillariasis (caused by C. philippinensis) manifests as abdominal pain and diarrhea, which, if untreated, may become severe because of autoinfection. A protein-losing enteropathy can develop which may result in cachexia and death.
Capillaria philippinensis eggs.
Figure A: Egg of C. philippinensis in an unstained wet mount of stool.
Figure B: Egg of C. philippinensis in an unstained wet mount of stool.
Figure C: Egg of C. philippinensis in an unstained wet mount of stool.
Figure D: Egg of C. philippinensis in an unstained wet mount of stool.
Capillaria philippinensis adults.
Figure A: Longitudinal section of an adult of C. philippinensis from an intestinal biopsy specimen stained with hematoxylin and eosin (H&E).
Figure B: Longitudinal section of an adult of C. philippinensis from an intestinal biopsy specimen stained with hematoxylin and eosin (H&E).
Figure C: Longitudinal section of an adult C. philippinensis from an intestinal biopsy specimen, stained with H&E.
Figure D: Higher magnification of Figure C, showing stichocytes within the adult worm.
Figure E: Cross-section of a gravid adult female C. philippinensis from an intestinal biopsy specimen, stained with H&E. Shown in this figure are a bacillary band (blue arrow), the intestine (red arrow) and uterus containing an egg in cross-section (black arrow).
The specific diagnosis of C. philippinensis is established by finding eggs, larvae and/or adult worms in the stool, or in intestinal biopsies. Unembryonated eggs are the typical stage found in the feces. In severe infections, embryonated eggs, larvae, and even adult worms can be found in the feces.
Treatment information for intestinal capillariasis can be found at: https://www.cdc.gov/parasites/capillaria/health_professionals/index.html
DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.
- Page last reviewed: December 14, 2017
- Page last updated: December 14, 2017
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