8/8/2019 Cap Ill Aria

http://slidepdf.com/reader/full/cap-ill-aria 1/5

Causal Agents:

The nematode (roundworm) Capillaria philippinensis causes human intestinal capillariasis.Two other Capillaria species parasitize animals, with rare reported instances of humaninfections. They are C. hepatica, which causes in humans hepatic capillariasis, and C.

aerophila, which causes in humans pulmonary capillariasis.

Life Cycle:

Typically, unembryonated eggs are passed in the human stool and 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 host . 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 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 worms) . Capillaria philippinesis is currently

considered a parasite of fish eating birds, which seem to be the natural definitive host .

 

8/8/2019 Cap Ill Aria

http://slidepdf.com/reader/full/cap-ill-aria 2/5

Capillaria hepatica has a direct life cycle that requires only one host. Adult worms invadethe liver of the host (usually rodents, but may also be pigs, carnivores and primates,

including humans), and lay hundreds of eggs in the surrounding parenchyma . The eggs

are not passed in the feces of the host, and remain in the liver until the animal dies anddecomposes , or is eaten by a predator or scavenger . Eggs ingested by such an animalare unembryonated, are not infectious, and are passed in the feces, providing an efficient

mechanism to release eggs into the environment . Cannibalism has been reported as an

important role in transmission among rodent populations. Eggs embryonate in the

environment , where they require air and damp soil to become infective. Under optimalconditions, this takes about 30 days. The cycle continues when embryonated eggs are

eaten by a suitable mammalian host . Infective eggs hatch in the intestine, releasing

larvae. The larvae migrate via the portal vein to the liver. Larvae take about four weeks tomature into adults and mate. Humans are usually infected after ingesting embryonated

eggs in fecal-contaminated food, water, or soil . Occasionally in humans, larvae will

migrate to the lungs, kidneys, or other organs. The presence of C . hepatica eggs in human

stool during routine ova-and-parasite (O&P) examinations indicates spurious passage of ingested eggs, and not a true infection. Diagnosis in humans is usually achieved by findingadults and eggs in biopsy or autopsy specimens.

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. Rarecases of human infections with C. hepatica and C. aerophila have been reported worldwide.

Clinical Features: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. Hepaticcapillariasis (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.

Laboratory Diagnosis:The specific diagnosis of C. philippinensis is established by finding eggs, larvae and/or adult worms inthe 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.

8/8/2019 Cap Ill Aria

http://slidepdf.com/reader/full/cap-ill-aria 3/5

The specific diagnosis of C. hepatica infection is based on demonstrating the adult worms and/or eggsin liver tissue at biopsy or necropsy. (Note: identification of C. hepatica eggs in the stool is a spuriousfinding, which does not result from infection of the human host, but from ingestion by that host of livers from infected animals.)The specific diagnosis of C. aerophila is based on demonstrating eggs in stool or in lung biopsy.

Diagnostic findings

Microscopy

Morphologic comparison with other intestinal parasites

Treatment:The drug of choice is mebendazole*, and albendazole* is an alternative. For additional

information, see the recommendations in The Medical Letter (Drugs for Parasitic

Infections).

* This drug is approved by the FDA, but considered investigational for this purpose.

Microscopy

A B

A, B:  Capillaria philippinensis eggs. These unembryonated eggs measure 35 to 45 µm in

length by 20-25 µm in width. They have two inconspicuous polar prominences and astriated shell.

8/8/2019 Cap Ill Aria

http://slidepdf.com/reader/full/cap-ill-aria 4/5

C D

C , D:  Capillaria hepatica eggs in liver, stained with hematoxylin and eosin (H&E). Eggs of C. hepatica are 50-70 µm long by 30-35 µm wide and are unembryonated when seen in

human stool (an indication of a spurious infection).

E F

E: Longitudinal section of an adult C. philippinensis in an intestinal biopsy specimen,

stained with H&E, showing stichocytes.F: Cross section of a gravid adult female C. philippinensis in an intestinal biopsy specimen,

stained with H&E. Shown here are a bacillary band (blue arrow), the intestine (red arrow)and the uterus containing an egg in cross-section (black arrow).

8/8/2019 Cap Ill Aria

http://slidepdf.com/reader/full/cap-ill-aria 5/5

G H

G: Cross section of a male C. hepatica in liver tissue, stained with H&E. Note the presence

of the intestine (blue arrow) and the coiled sections of the testes (black arrows).

H: Cross section of C. hepatica in liver tissue, stained with H&E. Note the presence of theintestine (blue arrow) and bacillary bands (black arrows).