Chagas vector — DTM&H MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: C — Triatomine bug
The correct answer is C, Triatomine bug, because Chagas disease (American trypanosomiasis, caused by Trypanosoma cruzi) is transmitted by nocturnal triatomine (reduviid) bugs that live in cracks in mud walls or thatched roofs and defaecate near the bite wound after feeding, allowing the parasite to enter through the bite site or mucosa when the person scratches. This matches every discriminator in the stem: Bolivia is a highly endemic country, the insects are described as nocturnal and living in wall cracks, and they defaecate near the bite (the classic mechanism of transmission, distinct from a simple bite-borne infection). Chronic infection produces dilated cardiomyopathy and mega-oesophagus/mega-colon years after the initial exposure, explaining the cardiomyopathy clusters in the vignette. Poor rural housing (mud brick, thatch) is the key risk factor exploited by this domestic vector. Why the other options are wrong: B. Blackfly: transmits Onchocerca volvulus (onchocerciasis), causing skin and eye disease, not cardiomyopathy, and does not defaecate at the bite site. D. Tsetse fly: transmits African trypanosomiasis (sleeping sickness), confined to sub-Saharan Africa, not South America, and transmission is via direct bite inoculation of saliva, not faecal contamination. E. Aedes mosquito: transmits arboviruses (dengue, Zika, yellow fever) and does not live in wall cracks or transmit by defaecation; these present with febrile illness, not chronic cardiomyopathy. A. Sandfly: transmits Leishmania species, causing cutaneous, mucocutaneous or visceral leishmaniasis, not cardiac disease, and again transmits via bite inoculation, not faecal contamination. Key point: nocturnal wall-dwelling bugs that defaecate near the bite site in Latin America signal Trypanosoma cruzi transmission by triatomine bugs, leading to Chagas cardiomyopathy.
Reference: GOV.UK, Chagas disease: migrant health guide (UKHSA), 2025, https://www.gov.uk/guidance/chagas-disease-migrant-health-guide