Question
Write briefly on the pathogenesis, clinical features and laboratory diagnosis of Ascariasis. (3+2+3)
Answer
Pathogenesis of ascariasis (Ascaris lumbricoides, the largest human intestinal nematode) Faecal-oral ingestion of embryonated eggs from contaminated soil/food/water; larvae hatch in the small intestine, 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. Adult worms live free in the intestinal lumen without attaching to the mucosa.
Clinical features
- Pulmonary phase (Löffler’s syndrome) — cough, dyspnoea, wheeze, eosinophilic pneumonitis during larval lung migration, with marked peripheral eosinophilia.
- Intestinal phase — usually asymptomatic with light infection; heavy worm burden can cause abdominal discomfort, malnutrition, and intestinal obstruction (a bolus of worms), particularly in children.
- Complications from aberrant migration — biliary/pancreatic duct obstruction (cholangitis, pancreatitis), appendicitis, or, rarely, migration through the mouth/nose.
Laboratory diagnosis
- Stool microscopy — for characteristic fertilized eggs (mammillated outer coat, bile-stained brown, single large ovum) or unfertilized eggs (more elongated, thinner-shelled, lacking mammillation, containing disorganized granules).
- Adult worms occasionally passed spontaneously, or visualized as filling defects on barium studies.
- Peripheral eosinophilia — a supportive but non-specific finding, particularly during the pulmonary migratory phase.
Treatment: albendazole or mebendazole; surgical intervention for obstructive complications.