Ascariasis (roundworm infection)
Ascariasis is fecal-oral infection with Ascaris lumbricoides, the largest intestinal nematode, treated with albendazole 400 mg single dose; it causes Loffler pulmonary eosinophilia during larval lung migration and, with heavy adult worm burden, intestinal, biliary, or pancreatic duct obstruction.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Fecal-oral nematode infection: ascariasis is caused by Ascaris lumbricoides, the largest of the intestinal nematodes (roundworms), acquired by ingesting embryonated eggs from soil, contaminated…
- Epidemiology
Most common human helminth infection worldwide: highest prevalence in areas with poor sanitation in tropical and subtropical regions of Asia, sub-Saharan Africa, and Latin America.
- Risk factors
Poor sanitation and open defecation: the dominant driver, since human feces is the sole source of infective eggs contaminating soil.
- Pathophysiology
Ingestion of embryonated eggs: eggs hatch in the small intestine, releasing larvae.
- Clinical features
Most infections are asymptomatic: light burdens frequently produce no symptoms and are found incidentally on stool exam.
- Differential diagnosis
Hookworm infection: cutaneous larva-penetration site (ground itch) and iron-deficiency anemia from chronic blood loss, not obstruction; see hookworm infection.
- Diagnosis
Confirmed by identifying the organism: stool ova and parasite microscopy showing the characteristic knobby (mammillated), oval, bile-stained eggs is the standard confirmatory test; a visibly passed adult worm is also diagnostic.
- Management
Uncomplicated intestinal infection: albendazole 400 mg PO as a single dose, the first-line treatment.
- Complications
Intestinal obstruction: most often at the ileocecal valve from a bolus of adult worms, most common and most severe in children with heavy worm burden.
- Prognosis
Excellent with treatment in uncomplicated disease: antihelminthic therapy is highly effective and light infections resolve without sequelae.
- Prevention
Improved sanitation and safe excreta disposal: the definitive long-term prevention measure, breaking the fecal-soil-oral transmission cycle.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Hookworm infection
Hookworm infection, caused by Necator americanus or Ancylostoma duodenale, is treated with albendazole 400 mg single dose plus iron repletion; it is acquired when soil larvae penetrate bare skin and produces microcytic iron-deficiency anemia from chronic intestinal blood loss by adult worms attached to the small bowel mucosa.
- Trichuriasis (whipworm infection)
Trichuriasis is fecal-oral infection of the colon with Trichuris trichiura (whipworm), treated with albendazole 400 mg daily for 3 days; light infection is often asymptomatic, while heavy pediatric worm burden causes chronic dysentery, growth impairment, and rectal prolapse.
- Strongyloidiasis
Strongyloides stercoralis is a soil-transmitted nematode uniquely capable of autoinfection, so it can persist for decades and, in a host started on glucocorticoids or otherwise immunosuppressed, progress to hyperinfection with gram-negative bacteremia; diagnosis is by stool larvae or serology and treatment is ivermectin.
- Pinworm infection (enterobiasis)
Pinworm infection (enterobiasis) is caused by the nematode Enterobius vermicularis and is the most common helminthic infection in children, presenting with perianal pruritus that is worse at night. Diagnosis is made by the cellophane tape test performed on first waking, and treatment is a single oral dose of albendazole, mebendazole, or pyrantel pamoate given to the patient and all household members, repeated after two weeks to break the autoinfection cycle.
- Trichinellosis
Trichinellosis is infection with Trichinella spiralis larvae acquired from undercooked meat, especially pork or wild game, producing an initial intestinal illness followed by larval encystment in striated muscle causing myositis, periorbital edema, and eosinophilia. Diagnosis rests on eosinophilia and elevated creatine kinase confirmed by serology or muscle biopsy, and treatment combines an antihelminthic with corticosteroids for severe systemic disease.
- Toxocariasis
Toxocariasis is human infection with the dog or cat roundworm Toxocara canis or Toxocara cati, acquired by ingesting embryonated eggs, producing visceral larva migrans with hepatic, pulmonary, and eosinophilic disease or ocular larva migrans mimicking retinoblastoma. Diagnosis rests on compatible exposure and clinical findings plus Toxocara-specific serology, and treatment combines an antihelminthic with corticosteroids for organ-threatening inflammation.