Capillaria (C. philippinensis, C. hepatica, C. aerophila)
- Parasite
- For completeness
Thread-thin worms related to whipworm. One lives in the gut after raw fish and can waste the body; others reach the liver or the lungs.
Also called: Paracapillaria philippinensis, Calodium hepaticum, Eucoleus aerophilus, capillariasis
Quick facts
- Type
- Parasite · Nematodes
- Gram / shape
- Very thin worms
- Spread
- C · C · C
- Causes
- Intestinal capillariasis · Hepatic capillariasis
- Treatment
- Benzimidazoles
At a glance
- Shape
- Very thin worms; barrel-shaped eggs with two flattened polar plugs and a striated shell
- Family
- Capillariidae
- Type
- Trichuroid nematodes (roundworms related to Trichuris)
- Size
- C. philippinensis adults about 2–4.5 mm; its eggs 35–45 × 20–25 µm; C. hepatica eggs about 50–70 µm
Morphology
- Eggs look like small Trichuris eggs: barrel shape, two polar prominences, striated shell.
- C. philippinensis eggs are passed unembryonated; some females release shell-less eggs that hatch inside the gut.
- C. hepatica eggs stay trapped in liver tissue and are not passed in the stool of an infected person.
Transmission
- C. philippinensis: eating raw or undercooked small freshwater fish that carry larvae.
- C. hepatica: swallowing embryonated eggs from soil, food or water contaminated by dead rodents.
- C. aerophila: swallowing embryonated eggs, possibly earthworms, from the environment of foxes, dogs and cats.
Reservoir: C. philippinensis: freshwater fish (intermediate hosts); fish-eating birds proposed; C. hepatica: rats and other rodents; C. aerophila: foxes, dogs, cats and other carnivores
Isolation precautions
What the care team adds to standard precautions.
- Standard
Life cycle
- C. philippinensis eggs leave in stool and embryonate in water within days.
- Freshwater fish eat the eggs; larvae hatch and settle in the fish tissues.
- A person eats the raw fish; adults burrow into the small-intestine mucosa.
- Some larvae hatch inside the gut and reinvade it (autoinfection), so worm numbers can explode.
- C. hepatica: eggs freed when a rodent liver decays or is eaten embryonate in soil and are swallowed.
- In C. hepatica the adults live and lay eggs in the liver, which is why stool shows no true eggs.
Virulence factors
- Autoinfection lets C. philippinensis build huge worm burdens without new exposure.
- Mucosal invasion causes malabsorption and protein-losing enteropathy with low albumin and potassium.
- C. hepatica egg deposits cause granulomas and liver necrosis.
- C. aerophila in the airways causes bronchitis and can form masses that mimic cancer.
Diseases it causes
- Intestinal capillariasis: chronic watery diarrhoea, malabsorption and protein-losing enteropathy
- Hepatic capillariasis: acute or subacute hepatitis with fever, hepatomegaly and eosinophilia
- Pulmonary capillariasis: cough, mucoid or bloody sputum, fever (rare)
Clinical picture
- Intestinal form: borborygmi, abdominal pain, weeks of diarrhoea, weight loss, oedema and cachexia.
- Untreated intestinal disease can be fatal through electrolyte loss, heart failure and wasting.
- Hepatic form: fever, enlarged liver, leukocytosis and marked eosinophilia.
- Eggs of C. hepatica in stool after eating animal liver are a spurious passage, not disease.
Diagnosis
- C. philippinensis: eggs, larvae or adults in stool or small-bowel biopsy; repeated stool exams help.
- C. hepatica: worms or eggs in a liver biopsy or at autopsy.
- C. aerophila: eggs in sputum or stool, or worms in a lung or bronchial biopsy.
- No validated serology; eggs can be confused with Trichuris eggs.
Treatment
Benzimidazoles (albendazole or mebendazole), given for a long course because autoinfection causes relapse, plus fluid, electrolyte and protein replacement in intestinal disease.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Cook freshwater fish well; avoid raw small fish dishes in endemic areas.
- Hand hygiene and rodent control; wash vegetables grown near rodents.
- Treat a known case fully, since autoinfection keeps it going.
Test yourself
Think of the answer, then tap the question to see it.
How do people acquire Capillaria philippinensis?
By eating raw or undercooked small freshwater fish that carry the larvae.
Which feature lets C. philippinensis cause massive infections?
Autoinfection: larvae hatch inside the gut and reinvade the mucosa without new exposure.
What syndrome results from heavy intestinal capillariasis?
Chronic diarrhoea with malabsorption and protein-losing enteropathy, which can be fatal.
Why do Capillaria hepatica eggs in a stool sample usually not mean disease?
In true infection eggs stay in the liver; eggs in stool usually come from eating infected animal liver (spurious passage).
Connections
← Back to the group: Nematodes
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: CDC - DPDx - Intestinal Capillariasis (CDC, 2020); CDC - DPDx - Hepatic Capillariasis (CDC, 2019); Molecular Detection of Capillaria aerophila, an Agent of Canine and Feline Pulmonary Capillariosis (Journal of Clinical Microbiology (PMC), 2012).
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Representative model, for educational purposes only.