East African trypanosomiasis — DTM&H MCQ

Correct answer: D — East African trypanosomiasis due to Trypanosoma brucei rhodesiense

A) East African trypanosomiasis due to Trypanosoma brucei rhodesiense is correct. This subspecies causes an acute, rapidly progressive zoonotic infection acquired from tsetse fly bites in East African game parks and savannah regions, exactly the exposure described for a Tanzanian safari guide. A painful, indurated chancre at the bite site within days, followed within one to two weeks by fever, severe headache and tachycardia with trypanosomes visible on a blood film, is the classic acute haemolymphatic presentation of T. b. rhodesiense, which multiplies rapidly and invades the bloodstream and CNS far sooner than T. b. gambiense. The short incubation, systemic toxicity and painful chancre are the key discriminators pointing to the rhodesiense form rather than a chronic gambiense course. Why the other options are wrong: B. West African trypanosomiasis due to Trypanosoma brucei gambiense: this form is transmitted in West and Central Africa, not Tanzania, and typically causes an indolent illness evolving over months to years, without the acute febrile chancre syndrome described. E. American trypanosomiasis due to Trypanosoma cruzi: transmitted by triatomine (reduviid) bugs in Latin America, not tsetse flies, and presents with a chagoma or Romana sign, not a tsetse-associated chancre; blood film trypomastigotes differ morphologically. A. Visceral leishmaniasis due to Leishmania donovani: caused by sandfly bites, presents with prolonged fever, hepatosplenomegaly and pancytopenia over weeks to months; no chancre and no motile trypanosomes on film, as amastigotes are intracellular. C. Relapsing fever due to Borrelia duttonii: transmitted by soft ticks in East Africa with recurrent fevers, but blood film shows spirochaetes, not trypanosomes, and there is no chancre. Key point: a painful chancre with acute fever soon after a tsetse fly bite in East Africa, plus trypanosomes on blood film, signals T. b. rhodesiense, which demands urgent staging and treatment given its rapid progression to CNS disease.

Reference: NaTHNaC (National Travel Health Network and Centre), travelhealthpro.org.uk, Trypanosomiasis disease page, https://travelhealthpro.org.uk/disease/214/trypanosomiasis