The dengue fever is caused by the bite of which of the following mosquitoes ?

Question

UnlockIAS · Accepted Answer

Correct — A, Aedes. Dengue is caused by the dengue virus, a flavivirus with four serotypes (DENV-1 to DENV-4), and it reaches humans through the bite of an infected female mosquito of the genus Aedes. The principal vector worldwide and in India is Aedes aegypti, a small dark mosquito with white markings that bites by day — typically in the hours after sunrise and before sunset — and breeds in clean, standing water collected in domestic containers: coolers, overhead tanks, flowerpot trays, discarded tyres and construction pits. The same genus carries chikungunya, Zika and yellow fever, which is why urban vector control targets Aedes breeding sites rather than the marshes and paddy fields associated with other mosquitoes. This item does, however, contain a real overlap that a careful candidate will notice: option (c), the Asian tiger mosquito, is Aedes albopictus, a genuine secondary vector of dengue and therefore itself a member of the genus named in option (a). Option (a) remains the answer because it names the whole genus, including the dominant vector Aedes aegypti, while option (c) names one species inside it — but a candidate who marked (c) had a defensible case, and this is one of the items in the 2022 paper where more than one option can be argued.

Why the other options are wrong — (b) Anopheles is the malaria mosquito. Female Anopheles transmit Plasmodium parasites — falciparum, vivax and others — and their habits differ from Aedes at almost every point: they bite mainly from dusk to dawn, rest at a characteristic angle to the surface, and breed in relatively clean natural water bodies such as pools, paddy fields, stream margins and seepages. Anopheles has no role in dengue transmission.  (c) This is the option that makes the question defective rather than merely difficult, and it should not be dismissed with a false statement. The Asian tiger mosquito is Aedes albopictus, and it genuinely does transmit dengue — it is the recognised secondary vector, important in rural and peri-urban settings and the species responsible for spreading dengue into new regions. It is therefore not wrong; it is simply a species within the genus that option (a) names, and the epidemiologically dominant dengue vector, Aedes aegypti, is a different species of that same genus. UPPSC's key takes the genus-level answer, so the mark goes to (a).  (d) Culex mosquitoes transmit Japanese encephalitis, lymphatic filariasis and West Nile fever — Culex tritaeniorhynchus is the classic Japanese encephalitis vector in the rice-growing belt, and Culex quinquefasciatus the filariasis vector of Indian towns, breeding in dirty, organically polluted water such as drains and cesspits. Filariasis in particular matters for Uttar Pradesh, but none of these diseases is dengue.

Concept: Vector-borne disease questions are answered by holding three columns together — the mosquito genus, the pathogen and the disease — because each genus has its own signature. Aedes carries viruses: dengue, chikungunya, Zika and yellow fever; it is a day-biter and breeds in clean water inside and around homes. Anopheles carries the malaria protozoan Plasmodium; it bites at night and breeds in clean natural water. Culex carries the Japanese encephalitis and West Nile viruses and the filarial worm Wuchereria bancrofti; it bites at night and breeds in polluted water. Those habits dictate the control strategy: source reduction and weekly dry-day campaigns against Aedes, indoor residual spraying and insecticide-treated nets against Anopheles, and drainage and sanitation against Culex. Dengue itself is worth understanding beyond the vector — infection with one serotype gives lasting immunity only to that serotype, and a subsequent infection with a different one carries a higher risk of severe dengue, which is why the disease is dangerous in areas where several serotypes circulate.

State PCS 2022 Q69 — Science & Technology PYQ with Answer

State PCS 2022 Q69 — Science & Technology PYQ with Answer