West African trypanosomiasis — DTM&H MCQ

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HardOther protozoal infectionsWest African trypanosomiasisDTM&H

A 51-year-old man from the Democratic Republic of Congo has months of daytime somnolence, behavioural change and intermittent fever. Cervical lymph nodes are enlarged and trypanosomes are detected in lymph-node aspirate. What is the most appropriate next investigation?

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Correct answer: C — Lumbar puncture to stage central nervous system involvement

The correct answer is C, lumbar puncture to stage central nervous system involvement. This man has confirmed human African trypanosomiasis (trypanosomes seen on lymph-node aspirate, classic Winterbottom's sign of cervical lymphadenopathy), and his months of somnolence and behavioural change strongly suggest second-stage (meningoencephalitic) disease. Once trypanosomes are identified, the essential next step is CSF examination by lumbar puncture, because treatment choice (pentamidine or fexinidazole for haemolymphatic first-stage disease versus regimens active against CNS disease, such as fexinidazole in eligible patients, NECT or melarsoprol) is dictated by CSF white cell count and the presence of trypanosomes in CSF. Staging is mandatory before treatment and cannot be inferred from symptoms alone. Why the other options are wrong: A. Stool microscopy for cysts: relevant to intestinal protozoa or helminths, not to trypanosomiasis, and does not influence HAT management. B. Urine antigen for Schistosoma haematobium: tests for a different parasite causing urogenital schistosomiasis; irrelevant once trypanosomes are already confirmed on microscopy. E. Dengue NS1 antigen: dengue causes acute febrile illness with a much shorter course and is not consistent with months of somnolence and confirmed trypanosomes. D. Skin snip microscopy: used to diagnose onchocerciasis (microfilariae), not trypanosomiasis, and adds nothing once the diagnosis is already made on lymph-node aspirate. Key point: In confirmed human African trypanosomiasis, lumbar puncture with CSF cell count and microscopy is mandatory to stage disease and determine the correct drug regimen.

Reference: WHO Guidelines for the Treatment of Human African Trypanosomiasis (NCBI Bookshelf, updated with fexinidazole recommendations): staging by CSF white cell count and trypanosome detection via lumbar puncture determines treatment choice. https://www.ncbi.nlm.nih.gov/books/NBK604900/