Triatomine domestic control — DTM&H MCQ

Correct answer: A — Residual insecticide spraying and housing improvement

Option A, residual insecticide spraying and housing improvement, is correct because the vignette describes classic domiciliary triatomine ecology: bugs colonising adobe wall cracks and thatched roofs, the microhabitats that sustain house infestation and vectorial transmission of Trypanosoma cruzi. Integrated vector control in Chagas disease endemic areas relies on pyrethroid residual spraying of infested dwellings combined with structural improvements (plastering walls, replacing thatch) that eliminate the crevices triatomines need to nest and blood-feed at night. This dual approach interrupts transmission at its source, the peridomestic bug population, rather than treating disease after exposure, and is the standard public health intervention recommended for rural Latin American Chagas control programmes. No vaccine or chemoprophylactic drug exists for prevention, making environmental and vector-targeted measures the only effective primary prevention strategy. Why the other options are wrong: C. Larvicide in rice paddies: this targets mosquito breeding sites relevant to malaria or arboviral disease control, not triatomine bugs, which are terrestrial, nocturnal, house-dwelling insects with no aquatic larval stage. D. Bed nets for blackfly bites: blackflies transmit onchocerciasis, not Chagas disease, and bed nets do not exclude triatomines, which bite exposed skin at night regardless of netting unless it is insecticide treated and specifically deployed against this vector. E. Dog vaccination campaign: there is no licensed vaccine against Trypanosoma cruzi for dogs or humans; dogs are a reservoir host but the intervention needed is vector and housing control, not immunisation. B. Molluscicide in lakes: this targets snail intermediate hosts relevant to schistosomiasis, entirely unrelated to a terrestrial reduviid bug vector. Key point: Chagas disease prevention centres on integrated vector control of triatomine bugs through residual insecticide spraying and housing improvement, since no vaccine or prophylactic drug exists.

Reference: PAHO/WHO, Chagas disease, Prevention and control: integrated vector control including insecticide spraying of infested homes and housing improvement, https://www.paho.org/en/topics/chagas-disease