Gambiense sleeping sickness — DTM&H MCQ

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HardProtozoal infectionsGambiense sleeping sicknessDTM&H

A 44-year-old man from northern Uganda has months of intermittent fever, pruritus and cervical lymphadenopathy. He later develops reversed sleep pattern and personality change. What is the vector or intermediate host most relevant to this infection?

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Correct answer: B — Glossina tsetse fly

The correct answer is B, Glossina tsetse fly. This vignette describes human African trypanosomiasis (sleeping sickness): a Ugandan patient with intermittent fever, pruritus, cervical lymphadenopathy (Winterbottom's sign), followed by reversed sleep-wake cycle and personality change as the parasite crosses into the CNS. Trypanosoma brucei is transmitted to humans by the bite of an infected tsetse fly, and northern Uganda is a recognised focus for both gambiense and rhodesiense disease. The tsetse fly is the definitive biological vector (the parasite develops within it before transmission), which is why it is the vector uniquely linked to this clinical picture rather than a bystander insect. No other vector produces this combination of chancre, posterior cervical lymphadenopathy, and progressive meningoencephalitic sleep disturbance. Why the other options are wrong: A. Simulium blackfly: this is the vector for onchocerciasis (river blindness), causing pruritic dermatitis and nodules, not fever with lymphadenopathy or CNS sleep disturbance. C. Aedes mosquito: transmits arboviruses (dengue, yellow fever, chikungunya) and does not cause a chronic relapsing febrile illness progressing to meningoencephalitis. E. Triatomine bug: vector for Chagas disease (Trypanosoma cruzi), which is confined to the Americas, not Uganda, and causes cardiomyopathy or megacolon, not sleeping sickness. D. Phlebotomine sandfly: transmits leishmaniasis, presenting with fever, hepatosplenomegaly and pancytopenia (visceral) or skin ulcers (cutaneous), not the reversed sleep pattern seen here. Key point: intermittent fever with posterior cervical lymphadenopathy progressing to reversed sleep-wake cycle in an East/Central African patient points to tsetse fly-borne trypanosomiasis, not the other vector-borne tropical diseases.

Reference: WHO Fact Sheet, Trypanosomiasis, human African (sleeping sickness), 2023, https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness)