Culex filariasis vector — DTM&H MCQ

Correct answer: E — Culex quinquefasciatus

The correct answer is E, Culex quinquefasciatus. This mosquito is the dominant vector of Wuchereria bancrofti in urban and peri-urban East African coastal settings, and it characteristically breeds in polluted, nutrient-rich water such as blocked drains, pit latrines and stagnant sewage rather than clean water. It is a strongly night-biting (nocturnal, endophagic) species, matching the entomological survey findings in the stem. Bancroftian filariasis with chronic manifestations such as hydrocoele is classically an urban disease pattern precisely because Culex thrives in the polluted breeding sites generated by dense, poorly sanitated coastal cities, distinguishing it from the rural, clean-water breeding Anopheles vectors also capable of transmitting W. bancrofti in parts of Africa. Why the other options are wrong: D. Aedes albopictus: This is a day-biting (diurnal) mosquito that breeds in clean water in containers and tyres, and it is chiefly an arbovirus vector (dengue, chikungunya), not a principal filariasis vector in this setting. B. Glossina morsitans: This is the tsetse fly, a savanna-dwelling biting fly transmitting African trypanosomiasis, not a mosquito, and unrelated to filariasis or polluted urban water breeding. A. Lutzomyia longipalpis: This is a New World sandfly vector of visceral leishmaniasis found in the Americas, not present in East Africa and not a mosquito. C. Simulium damnosum: This is a blackfly that breeds in fast-flowing, well-oxygenated rivers (not polluted stagnant water) and transmits onchocerciasis, presenting with skin and eye disease rather than hydrocoele. Key point: Urban lymphatic filariasis with hydrocoele in polluted, stagnant coastal water and night-biting mosquitoes points to Culex quinquefasciatus, the classic urban vector of Wuchereria bancrofti.

Reference: World Health Organization, Lymphatic filariasis fact sheet (2024): 'Lymphatic filariasis is transmitted by different types of mosquitoes, for example by the Culex mosquito, widespread across urban and semi-urban areas...' https://www.who.int/news-room/fact-sheets/detail/lymphatic-filariasis