Wolbachia-based dengue control — DTM&H MCQ
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Correct answer: C — Wolbachia reduces mosquito ability to transmit dengue virus
The correct answer is C, Wolbachia reduces mosquito ability to transmit dengue virus. Wolbachia is an intracellular bacterium that, once established in Aedes aegypti, interferes with dengue viral replication through competition for host cell resources (particularly cholesterol and lipids) and upregulation of the mosquito innate immune system. This lowers vector competence so that infected mosquitoes carry a much lower dengue viral load and are far less likely to transmit virus at a subsequent bite, without the mosquito needing to die or stop biting. Field deployment (World Mosquito Program wMel releases) has demonstrated substantial reductions in symptomatic dengue incidence in released areas, and self-sustaining spread is driven separately by cytoplasmic incompatibility, which is the spread mechanism rather than the transmission-blocking mechanism itself. Why the other options are wrong: D. Sterilises female mosquitoes: Wolbachia does not sterilise females; it causes cytoplasmic incompatibility, meaning eggs from uninfected females mated with infected males fail to develop, which drives population replacement, not sterility of the released strain's own females. A. Produces a dengue-toxic substance: There is no known Wolbachia-derived toxin that directly kills dengue virus; the effect is via resource competition and immune priming, not a toxic metabolite. B. Shifts feeding to animals: Wolbachia infection does not alter Aedes aegypti host-feeding preference, which remains strongly anthropophilic; this is not a described mechanism. E. Shortens lifespan below the EIP: Life-shortening was a feature of the earlier wMelPop strain studied experimentally, but the strain used in current field programmes (wMel) is chosen for lower fitness cost and stable establishment, and the transmission-blocking effect operates independently of lifespan reduction. Key point: Wolbachia blocks dengue transmission chiefly by directly reducing the virus's ability to replicate and be transmitted within the mosquito (reduced vector competence), not by killing, sterilising, or behaviourally altering the mosquito.
Reference: Cochrane Review / PMC: 'Wolbachia-carrying Aedes mosquitoes for preventing dengue infection', PMC9983298 (2023), https://pmc.ncbi.nlm.nih.gov/articles/PMC9983298/