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What is the Most Likely Culprit Organism ?
A 2-year-old boy from a rural village was brought to the pediatric clinic with a 6-month history of diarrhea and poor weight gain. His body weight was 12.1 kg (below the 25th percentile for his age) and height 90 cm (1 SD below the median for his age). Physical examination revealed dry mucous membranes and decreased skin turgor. Laboratory tests showed iron-deficiency anemia, eosinophilia, and occult blood in the stool. Stool samples examined by direct microscopy for ova and parasites were negative. A colonoscopy showed numerous mobile, white worms adherent to the colon wall. What is the most likely culprit organism?
Options:
Ascaris lumbricoides
Enterobius vermicularis (pinworm)
Hymenolepis nana (dwarf tapeworm)
Strongyloides stercoralis
Trichuris trichiura (whipworm)
Correct Answer: Trichuris trichiura (Option 5)
🧠 Key Insight: Trichuris trichiura is the only worm that matches the location (colon), chronic blood loss, diarrhea, and colonoscopy findings of adherent worms
Ingestion of embryonated eggs
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Eggs hatch in the small intestine 🧠
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Larvae migrate to colon 🧠
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Mature into adult worms 🧠
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Worms attach to colon mucosa
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Mechanical damage to mucosa 🧠
⬇️ Nutrient absorption
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Mucosal damage causes chronic blood loss
⬇️ Iron stores ⬇️ Hemoglobin ⬇️ Red blood cell production
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🧠 Result: Iron-deficiency anemia
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Chronic diarrhea due to mucosal disruption 🧠
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⬇️ Fluid absorption ⬇️ Electrolyte balance
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🧠 Result: Dehydration, poor weight gain
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Immune response to parasitic infection ⬆️ Eosinophils 🧠
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Mucosal injury leads to occult blood in stool 🧠
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Colonoscopy reveals worms attached to colon 🧠
Why Other Answers Are Wrong?
Ascaris lumbricoides
🧠 Location: Typically resides in the small intestine, not the colon
🧠 Symptoms: Causes intestinal obstruction rather than chronic diarrhea and blood loss
🧠 No attachment to colon mucosa
Enterobius vermicularis (Pinworm)
🧠 Location: Found in the cecum, perianal area
🧠 Symptoms: Perianal itching, no chronic diarrhea, and no blood loss
🧠 Negative colonoscopy finding
Hymenolepis nana (Dwarf Tapeworm)
🧠 Location: Small intestine, not the colon
🧠 Symptoms: Usually asymptomatic or mild GI symptoms, no blood loss
🧠 No worms seen on colonoscopy
Strongyloides stercoralis
🧠 Location: Small intestine (larvae penetrate skin and migrate)
🧠 Symptoms: Includes pulmonary symptoms, no worms seen in colon
🧠 No large worms adhering to colon wall
Flashcards
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Dr. Shoaib Ahmad