Sandfly control — DTM&H MCQ
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Correct answer: D — Phlebotomine sandfly
D. Phlebotomine sandfly is correct because these are the small, hairy flies that transmit visceral leishmaniasis, and their described ecology (breeding in organic matter, resting in cracks in walls, houses and animal shelters) is the classic epidemiological fingerprint of Phlebotomus species in the Old World (and Lutzomyia in the New World). Female sandflies take a blood meal, ingesting amastigotes from an infected human or animal reservoir (commonly dogs), which develop into promastigotes and are inoculated into a new host at the next bite, completing transmission of Leishmania donovani or related species. The stem's morphological clue (small, hairy) and the behavioural clue (resting in cracks and animal shelters, reflecting endophilic/peridomestic resting habits) are specific to sandflies and are used precisely to distinguish them from other biting Diptera in exam vignettes. Why the other options are wrong: E. Tsetse fly: This is a larger, robust fly (not small and hairy) that transmits African trypanosomiasis, not leishmaniasis, and breeds in shaded riverine or woodland vegetation rather than cracks in dwellings. B. Aedes mosquito: Aedes species transmit arboviruses (dengue, chikungunya, Zika, yellow fever) via container breeding in clean water, and have no role in Leishmania transmission. C. Triatomine bug: These "kissing bugs" transmit Trypanosoma cruzi (Chagas disease) by defecating near a bite wound; although they also hide in cracks in poor-quality housing, they are large, winged bugs, not small hairy flies. A. Culex mosquito: Culex species transmit lymphatic filariasis, Japanese encephalitis and West Nile virus, breeding in stagnant water, and are unrelated to leishmaniasis transmission. Key point: Small, hairy sandflies (Phlebotomus/Lutzomyia) breeding in organic debris and resting in wall cracks or animal shelters are the vector of visceral leishmaniasis, distinguishing them from mosquitoes, tsetse flies and triatomine bugs.
Reference: Cochrane Database of Systematic Reviews (via NCBI PMC), 'Vector and reservoir control for preventing leishmaniasis', description of phlebotomine sandfly breeding and resting sites, https://pmc.ncbi.nlm.nih.gov/articles/PMC4561525/