Chagas disease — DTM&H MCQ
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Correct answer: D — Triatomine bug
The correct answer is D, Triatomine bug, because this vignette describes chronic Chagas disease caused by Trypanosoma cruzi, endemic to rural Bolivia and much of Latin America. The triatomine (reduviid, "kissing") bug transmits the parasite when it defecates near a bite wound or on mucosa, and the trypomastigotes then enter through the broken skin or conjunctiva. Chronic infection selectively damages the myenteric plexus and cardiac conduction tissue, producing the classic megasyndromes (megaoesophagus causing dysphagia, megacolon causing constipation) alongside dilated cardiomyopathy with conduction abnormalities such as right bundle branch block, exactly as described here. In endemic countries transmission to people occurs primarily via the infected faeces of this blood-sucking bug, which is the discriminating vector fact examiners want you to link to the rural South American setting and the gut plus cardiac phenotype. Why the other options are wrong: B. Tsetse fly: transmits African trypanosomiasis (sleeping sickness), causing encephalopathy and lymphadenopathy in sub-Saharan Africa, not gut megasyndromes or cardiomyopathy. C. Anopheles mosquito: transmits malaria (Plasmodium species), which causes fever, haemolysis and cerebral disease, not chronic dysphagia, constipation or dilated cardiomyopathy. E. Blackfly: transmits onchocerciasis (Simulium species carry Onchocerca volvulus), causing skin nodules and river blindness, unrelated to cardiac or gut pathology described. A. Sandfly: transmits leishmaniasis (cutaneous, mucocutaneous or visceral), presenting with skin ulcers, mucosal destruction or hepatosplenomegaly, not conduction delay or megacolon. Key point: rural Latin American origin plus megaoesophagus/megacolon plus dilated cardiomyopathy with conduction delay equals chronic Chagas disease, transmitted by the triatomine bug's infected faeces.
Reference: UKHSA/GOV.UK, Chagas disease: migrant health guide (updated 31 March 2025), https://www.gov.uk/guidance/chagas-disease-migrant-health-guide