A 28-year-old woman from Odisha with chronic diarrhea and anemia undergoes peripheral blood smear examination. The smear shows motile parasites with a characteristic undulating membrane. Which of the following statements about Trypanosoma is NOT true?

Explanation

## Trypanosoma — Blood Smear and Clinical Features ### Trypanosoma Species and Transmission **Key Point:** Trypanosoma rangeli is NOT the causative agent of Chagas disease. *Trypanosoma cruzi* causes Chagas disease. T. rangeli is a non-pathogenic trypanosome found in Central and South America. **High-Yield:** Distinction between the two major pathogenic Trypanosoma species: | Feature | T. brucei | T. cruzi | |---------|-----------|----------| | **Disease** | African sleeping sickness | Chagas disease (American trypanosomiasis) | | **Vector** | Tsetse fly (*Glossina*) | Reduviid bug (kissing bug) | | **Geographic distribution** | Sub-Saharan Africa | Central and South America | | **Blood smear finding** | Motile, slender forms with undulating membrane | Crescent-shaped, intracellular amastigotes | | **CNS involvement** | Yes (meningoencephalitis in late stage) | Rare; primarily cardiac/GI involvement | ### Morphology of T. brucei on Blood Smear 1. **Undulating membrane:** Extends the full length of the body, formed by fusion of flagellum with body wall 2. **Kinetoplast:** Large, DNA-containing organelle at the base of the flagellum; visible on Romanowsky staining 3. **Motility:** Highly motile, characteristic jerky movement 4. **Size:** 15–30 μm long, slender appearance **Clinical Pearl:** In African sleeping sickness, parasites cross the blood–brain barrier and cause meningoencephalitis ("sleeping sickness"), characterized by sleep disturbances, personality changes, and eventual coma if untreated. **Mnemonic:** **"T. brucei = Brain (CNS); T. cruzi = Cardiac (heart)"** — helps recall the primary organ involvement. ### Why T. rangeli Is Not Chagas Disease - T. rangeli is transmitted by reduviid bugs (same vector as T. cruzi) - However, T. rangeli is **non-pathogenic** in humans - It causes no disease and is considered a commensal infection - **Chagas disease is caused exclusively by T. cruzi**, not T. rangeli ### Correct Statements About Trypanosoma - **T. brucei gambiense:** Causes chronic West African sleeping sickness with CNS involvement ✓ - **Undulating membrane:** Extends full length of T. brucei body ✓ - **Kinetoplast:** DNA-containing organelle visible in blood smear forms ✓ [cite:Park 26e Ch 8]