Ascariasis

KEY FEATURES

Essentials of Diagnosis

• Transient cough, urticaria, pulmonary infiltrates

• Eosinophilia

• Nonspecific abdominal symptoms

• Eggs in stools; adult worms occasionally passed

General Considerations

• Ascaris lumbricoides is the most common intestinal helminth

• Infection follows ingestion of eggs in contaminated food

• Larvae hatch in the small intestine, penetrate into the bloodstream, migrate to lungs, and then back to the gastrointestinal (GI) tract, where they develop into adult worms

• Adult worms can be up to 40 cm long and live for 1–2 years

Demographics

• Causes ∼800 million infections, with 12 million acute cases and ≥ 10,000 deaths annually

• Prevalence is high wherever there is poor hygiene and sanitation or where human feces are used as fertilizer

• Heavy infections are most common in children

CLINICAL FINDINGS

Symptoms and Signs

• Most infected persons are asymptomatic

• The following symptoms develop in a small number of patients during migration of worms through the lungs

  • Fever

  • Nonproductive cough

  • Chest pain

  • Dyspnea

  • Eosinophilia

  • Eosinophilic pneumonia (occasionally)

• Rarely, larvae lodge ectopically in the brain, kidney, eye, spinal cord, and other sites and may cause local symptoms

• With heavy infection, abdominal discomfort may be seen

• Adult worms may migrate and be coughed up, vomited, or may emerge through the nose or anus

• They may also migrate into the common bile duct, pancreatic duct, appendix, and other sites, which may lead to

  • Cholangitis

  • Cholecystitis

  • Pyogenic liver abscess

  • Pancreatitis

  • Obstructive jaundice

  • Appendicitis

• With very heavy infestations, masses of worms may cause

  • Intestinal obstruction

  • Volvulus

  • Intussusception

  • Death

• Moderate to high worm loads in children are also associated with nutritional abnormalities

DIAGNOSIS

Laboratory Tests

• Diagnosis is made after adult worms emerge from the mouth, nose, or anus, or by identifying characteristic eggs in the feces, usually with the Kato-Katz technique

• Eosinophilia is marked during worm migration but may be absent during intestinal infection

Imaging Studies

• Plain abdominal films and ultrasonography can demonstrate worms, with filling defects in contrast studies and at times evidence of intestinal or biliary obstruction

TREATMENT

Medications

• All infections should be treated

• Treatments of choice

  • Albendazole (single 400-mg oral dose)

  • Mebendazole (single 500-mg oral dose or 100 mg twice daily for 3 days)

  • Pyrantel pamoate (single 11-mg/kg oral dose, maximum 1 g)

• All three of these drugs are

  • Well tolerated but may cause mild GI toxicity

  • Considered safe for children above 1 year of age and in pregnancy, although use in the first trimester is best avoided

• An alternative (but not in children < 35 kg or in pregnant people) is ivermectin (single 200-mcg/kg oral ...