(roundworm) 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.
unembryonated eggs are passed in the human stool
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
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
Capillaria philippinesis is currently considered a parasite of
fish eating birds, which seem to be the natural definitive host
adult worms reside in the liver of various animals, especially rats.
The females produce eggs that are retained in the liver parenchyma.
When the infected animal is eaten by another animal, the eggs are
released by digestion, excreted in the feces of the second animal, and
become embryonated in the soil. Alternately, the eggs can be released
following the death and decomposition of the first animal, and mature in
the soil. Following ingestion by a subsequent host, these infective
eggs release larvae in the intestine that migrate through the portal
circulation to the liver, where they develop into adults.
adult worms reside in the epithelium of the tracheo-bronchial tract of
various animals. Eggs are produced, coughed up, swallowed by the
animal, and excreted in its feces. The eggs become embryonated in the
soil. Ingestion of infective eggs completes the cycle. Transport or
paratenic hosts may also intervene in the cycle.
is endemic in the Philippines and also occurs in Thailand. Rare cases
have been reported from other Asian countries, the Middle East, and
Colombia. Rare cases of human infections with C. hepatica and
C. aerophila have been reported worldwide.
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. Hepatic capillariasis (C.
hepatica) manifests as an acute or subacute hepatitis with
eosinophilia, with possible dissemination to other organs. It may be
fatal. Pulmonary capillariasis (C. aerophila) may present with
fever, cough, asthma, and pneumonia, and also may be fatal.
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.
The specific diagnosis of C. hepatica infection is based on
demonstrating the adult worms and/or eggs in liver tissue at biopsy or
necropsy. (Note: identification of C. hepatica eggs in the stool
is a spurious finding, which does not result from infection of the human
host, but from ingestion by that host of livers from infected
The specific diagnosis of C. aerophila is based on demonstrating
eggs in stool or in lung biopsy.
comparison with other intestinal parasites
The drug of choice
is mebendazole*, and albendazole* is an alternative.
* This drug is
approved by the FDA, but considered investigational for this purpose.