Q1. What is Ascaris lumbricoides?
- Large intestinal roundworm of humans
- Causes ascariasis, common in tropical & subtropical areas
- Transmitted via fecal‑oral route (contaminated soil, food, water)
Q2. Morphology of the adult worm and egg
- Adult male: 15‑30 cm long, 3‑4 mm wide, curved tail, two posterior ventral alae
- Adult female: 20‑40 cm long, 5‑6 mm wide, straight tail, uterus filled with eggs
- Egg: oval, brownish, thick mamillated shell, 50‑70 µm × 30‑35 µm, contains single embryonated embryo
Q3. Life cycle (step‑wise, arrows show flow)
- Infected person passes eggs in feces →
- Eggs become embryonated in soil (≈2‑4 weeks) →
- Contaminated food, water or hands are ingested →
- Egg hatches in duodenum, releasing second‑stage larva →
- Larva penetrates intestinal wall → enters portal circulation →
- Reaches liver → passes to right heart → pulmonary artery → lungs →
- Larva breaks alveolar wall, ascends bronchial tree → swallowed →
- Returns to small intestine → matures into adult worm → starts laying eggs
Memory rhyme: “Feces → Soil → Swallow → Hatch → Travel → Lungs → Cough → Swallow → Grow”
Q4. Pathogenesis (step‑wise)
- Ingestion of embryonated eggs → hatching in gut
- Larval penetration → tissue injury in intestinal wall, liver, lungs
- Pulmonary migration → hemorrhage, eosinophilic pneumonitis, cough, wheeze
- Adult worms in lumen → mechanical obstruction, malabsorption, nutrient loss, vitamin A & iron deficiency
Q5. Clinical features
- Pulmonary phase (Loeffler’s syndrome): dry cough, wheeze, fever, eosinophilia, transient infiltrates on X‑ray
- Intestinal phase: abdominal pain, nausea, vomiting, diarrhoea, loss of appetite, weight loss, growth retardation in children
- Heavy infection: intestinal blockage, volvulus, perforation, peritonitis, biliary or pancreatic duct obstruction (rare)
Q6. Complications
- Acute intestinal obstruction → surgical emergency
- Malnutrition, anemia, vitamin A deficiency → impaired immunity, night‑blindness
- Hepatobiliary ascariasis → cholangitis, cholelithiasis
- Pulmonary fibrosis (chronic heavy infection)
Q7. Laboratory diagnosis
- Stool microscopy: direct wet mount or concentration technique → characteristic thick‑shelled, mamillated eggs (single embryo)
- Egg count (eggs per gram) for intensity grading (light <5 k, moderate 5‑20 k, heavy >20 k)
- Sputum examination (during pulmonary phase) may show larvae
- Serology (ELISA) – useful in ectopic or heavy infection, not routine
- Imaging: abdominal X‑ray/ultrasound shows “soap‑bubble” appearance of clustered worms in intestine; chest X‑ray shows fleeting infiltrates
Q8. Management (exam‑oriented)
- Albendazole 400 mg single dose OR Mebendazole 100 mg twice daily for 3 days (WHO regimen)
- Ivermectin 200 µg/kg single dose (alternative)
- For massive intestinal obstruction: nasogastric decompression, IV fluids, possible surgical removal of worm bolus
- Preventive measures:
• Proper disposal of human feces, latrine use
• Hand washing with soap after defecation and before meals
• Washing, peeling, cooking vegetables & fruits thoroughly
• Health education in schools, deworming programs (annual albendazole 400 mg for children 1‑15 yr)
Q9. Key exam points (Robbins, Harsh Mohan, Ananthanarayan, Chatterjee, NCH)
- Egg size & mamillated shell are diagnostic hallmarks
- Loeffler’s syndrome is the classic pulmonary manifestation of larval migration
- “Feces → Soil → Swallow → Hatch → Travel → Lungs → Cough → Swallow → Grow” helps recall the complete cycle
- Heavy worm load → mechanical obstruction, especially in children → surgical emergency
- Single‑dose albendazole is the drug of choice; repeat dose after 2 weeks for reinfection control
- Emphasize sanitation & periodic deworming as primary control strategy.