Capillariasis
Capillariasis is a disease caused by nematodes from the Capillaria genus, affecting the intestines, lungs, or liver. There are three primary forms of this infection: intestinal capillariasis caused by *C. philippinensis*, hepatic capillariasis caused by *C. hepatica*, and pulmonary capillariasis caused by *C. aerophila*. Infection typically occurs through the consumption of contaminated food, such as raw or undercooked fish, or through ingestion of soil or vegetables contaminated with feces. Symptoms vary depending on the type of capillariasis; intestinal infections may lead to diarrhea and abdominal pain, while hepatic infections can mimic acute hepatitis, and pulmonary infections often present with respiratory issues. Diagnosis is generally made by identifying eggs or adult worms in stool samples or tissues. Treatment usually involves anthelmintics like mebendazole or albendazole. Preventive measures focus on safe food handling, proper cooking, and maintaining good hygiene practices. Understanding these elements can help individuals mitigate the risk of capillariasis in susceptible regions.
Capillariasis
- ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, intestines, liver, lungs, respiratory system
Definition
Capillariasis is a disease of the intestines, lungs, or liver caused by nematodes (roundworms) belonging to the genus Capillaria.
Causes
There are three causes of human capillariasis: C. philippinensis, which causes intestinal capillariasis; C. hepatica, which causes hepatic capillariasis; and C. aerophila, which causes pulmonary capillariasis.
Humans become infected with intestinal capillariasis when they ingest raw and undercooked fish containing the C. philippinensis nematodes. These worms live in the small intestine and burrow into the mucosa. Female worms deposit unembryonated (noninfectious) eggs, some of which can become embryonated and can thus release larvae. Autoinfection with the larvae can result in hyperinfection with massive numbers of adult nematodes.
Infection with C. hepatica results from consuming food, water, or soil that has been contaminated with feces containing embryonated eggs. The infective eggs hatch in the intestine and release larvae. The larvae migrate to the liver, mature into adults, mate, and lay hundreds of unembryonated eggs that remain in the liver until the infected person dies. Eggs, subsequently eaten by an internal predator or scavenger, are passed in the feces into the environment, where they can then become embryonated.
Female C. aerophila deposit unembryonated eggs in the lungs of many domestic and wild animals. The eggs are coughed up, swallowed, and passed in the animal’s feces. Under favorable conditions, the eggs become embryonated in the soil, are ingested by earthworms, and hatch inside earthworms. Other animals become infected when they ingest the earthworms. Human infection results from ingestion of embryonated eggs in contaminated soil (such as through the consumption of vegetables not sufficiently washed). Once in the human host, the larvae migrate to the lungs and invade the mucosa.
Risk Factors
Eating raw or undercooked fish is a risk factor for intestinal capillariasis. The bite of an urban rodent is a risk factor for hepatic capillariasis because these rodents harbor C. hepatica eggs in their liver, which are natural reservoirs of the nematodes. Another risk factor for both hepatic and pulmonary capillariasis is consuming undercooked food, untreated water, or unwashed fruits and vegetables. In addition, increasing numbers of foxes and stray dogs and cats living in urban areas may increase the risk for pulmonary capillariasis.
Symptoms
The symptoms of intestinal capillariasis include watery diarrhea, abdominal pain, edema, weight loss, borborygmus (stomach growling), and decreased potassium and albumin levels in the blood. Hepatic capillariasis causes severe symptoms that mimic acute hepatitis. The clinical symptoms of pulmonary capillariasis are bronchitis, coughing, mucoid or blood-tinged sputum, fever, dyspnea, and eosinophilia.
People infected with a small number of C. hepatica worms often show no symptoms. As the infection advances, they may experience anemia, hepatitis, fever, and hypereosinophilia. If the diseases are not treated, they can be fatal.
Screening and Diagnosis
The diagnosis of human capillariasis usually involves finding the eggs or adults of C. philippinensis in stool samples. Hepatic capillariasis is diagnosed by the finding of the eggs or adult of C. hepatica in biopsy or autopsy specimens. Bronchial biopsies and sputum containing C. aerophila eggs or adults is helpful in the diagnosis of pulmonary capillariasis.
Treatment and Therapy
Capillariasis is treated with anthelmintics such as mebendazole, thiabendazole, and albendazole.
Prevention and Outcomes
Capillariasis can be prevented by avoiding the consumption of raw or undercooked fish and other foods, by avoiding drinking untreated water, and by cleaning fruits and vegetables thoroughly before eating.
Bibliography
"About Capillariasis." Centers for Disease Control, 23 Jan. 2024, www.cdc.gov/capillaria/about/index.html. Accessed 3 Feb. 2025.
Berger, Stephen A., and John S. Marr. Human Parasitic Diseases Sourcebook. Sudbury, Mass.: Jones and Bartlett, 2006.
Icon Health. Roundworms: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References.San Diego, Calif.: Author, 2004.
Roberts, Larry S., and John Janovy, Jr. Gerald D. Schmidt and Larry S. Roberts’ Foundations of Parasitology. 8th ed. Boston: McGraw-Hill, 2009.
Weller, P. F., and T. B. Nutman. “Intestinal Nematodes.” In Harrison’s Principles of Internal Medicine, edited by Joan Butterton. 17th ed. New York: McGraw-Hill, 2008.