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Intestinal Capillariasis

[Capillaria philippinensis]

Causal Agent

The nematode (roundworm) Capillaria philippinensis causes human intestinal capillariasis. 


Life Cycle

lifecycle

Typically,unembryonated eggs are passed in the human stool The number 1 and become embryonated in the external environment The number 2; after ingestion by freshwater fish, larvae hatch, penetrate theintestine, and migrate to the tissues The number 3. Ingestion of raw or undercooked fish results in infection of thehuman host. Humans are the only demonstrated hosts The number 4. 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 number 5. 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) The number 6. Capillaria philippinesis is currently considered aparasite of fish eating birds, which seem to be the natural definitive host The number 7.

Geographic Distribution

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.

Clinical Presentation

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.

 

Capillaria philippinensis eggs are 35 to 45 µm in length by 20-25 µm in width. They have two inconspicuous polar prominences and a striated shell. Eggs are unembryonated when passed in feces.
Figure A

Figure A: Egg of C. philippinensis in an unstained wet mount of stool.

Figure B

Figure B: Egg of C. philippinensis in an unstained wet mount of stool.

Figure C

Figure C: Egg of C. philippinensis in an unstained wet mount of stool.

Figure D

Figure D: Egg of C. philippinensis in an unstained wet mount of stool.

Capillaria philippinensis adults.

 

Capillaria philippinensis adult males are 2.0-3.5 mm in length and females are 2.5-4.5 mm in length. Females may contain embryonated or unembryonated eggs in utero. Fish-eating birds are the usual definitive host, but humans may harbor adults after consuming larvae in undercooked or raw fish.
Figure A

Figure A: Longitudinal section of an adult of C. philippinensis from an intestinal biopsy specimen stained with hematoxylin and eosin (H&E).

Figure B

Figure B: Longitudinal section of an adult of C. philippinensis from an intestinal biopsy specimen stained with hematoxylin and eosin (H&E).

Figure C

Figure C: Longitudinal section of an adult C. philippinensis from an intestinal biopsy specimen, stained with H&E.

Figure D

Figure D: Higher magnification of Figure C, showing stichocytes within the adult worm.

Figure E

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).

Diagnostic Findings

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.

More on: Morphologic comparison with other intestinal parasites

Treatment Information

Mebendazole*, is the drug of choice for adults, 200 mg orally twice a day for 20 days; the pediatric dosage is the same.

Alternative:

Albendazole*, adults, 400 mg orally once a day for 10 days; the pediatric dosage is the same.

(Note: Albendazole must be taken with food; a fatty meal increases oral bioavailability.)

Mebendazole

Mebendazole is available in the United States only through compounding pharmacies.

Mebendazole is in pregnancy category C. Data on the use of mebendazole in pregnant women are limited. The available evidence suggests no difference in congenital anomalies in the children of women who were treated with mebendazole during mass treatment programs compared with those who were not. In mass treatment programs for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of mebendazole in the 2nd and 3rd trimesters of pregnancy. The risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

It is not known whether mebendazole is excreted in breast milk. The WHO classifies mebendazole as compatible with breastfeeding and allows the use of mebendazole in lactating women.

The safety of mebendazole in children has not been established. There is limited data in children age 2 years and younger. Mebendazole is listed as an intestinal antihelminthic medicine on the WHO Model List of Essential Medicines for Children, intended for the use of children up to 12 years of age.

Albendazole

Oral albendazole is available for human use in the United States.

Albendazole is pregnancy category C. Data on the use of albendazole in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated with albendazole during mass prevention campaigns compared with those who were not. In mass prevention campaigns for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of albendazole in the 2nd and 3rd trimesters of pregnancy. However, the risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

It is not known whether albendazole is excreted in human milk. Albendazole should be used with caution in breastfeeding women.

The safety of albendazole in children less than 6 years old is not certain. Studies of the use of albendazole in children as young as one year old suggest that its use is safe. According to WHO guidelines for mass prevention campaigns, albendazole can be used in children as young as 1 year old. Many children less than 6 years old have been treated in these campaigns with albendazole, albeit at a reduced dose.

 

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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: May 3, 2016
  • Page last updated: May 3, 2016
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