Question
Ascariasis
Answer
Ascariasis, caused by Ascaris lumbricoides (the largest intestinal nematode infecting humans), is a soil-transmitted helminth infection acquired by faecal-oral ingestion of embryonated eggs from contaminated soil/food/water.
Life cycle: ingested eggs hatch in the small intestine, releasing larvae that penetrate the gut wall, enter the bloodstream, and undergo a hepato-pulmonary migration — liver, then lungs, where they enter alveoli, ascend the bronchial tree/trachea, and are swallowed, returning to the small intestine to mature into adult worms over 2–3 months.
Clinical features: pulmonary phase (Löffler’s syndrome) — cough, dyspnoea, eosinophilic pneumonitis during larval lung migration; intestinal phase — usually asymptomatic with light infection, but heavy worm burden can cause intestinal obstruction, malnutrition, and complications from aberrant worm migration (biliary/pancreatic duct obstruction, appendicitis).
Laboratory diagnosis: stool microscopy for characteristic mammillated, bile-stained fertilized eggs (or thinner-shelled unfertilized eggs).
Treatment: albendazole or mebendazole; surgical intervention for obstructive complications.