Spraying kerosene on stagnant water shall kill Anopheles due to

NORCET 3 - 2022 (Shift-2)

Community Health Nursing

Medium

Appeared in: NORCET 3 - 2022 (Shift-2)

Explanation

Kerosene is a mineral oil used as an anti-larval measure in vector control programs.
When sprayed on water, it forms a thin, non-permeable film on the surface.
Anopheles mosquito larvae and pupae are aquatic but breathe atmospheric air. They must regularly come to the surface to breathe through their spiracles (breathing pores).
The oil film physically blocks the spiracles, preventing the larvae from making contact with the air, leading to death by asphyxiation (suffocation).

Option B: The oil does not need to enter the respiratory tract. It works by creating an external barrier at the water's surface, preventing air from entering the spiracles in the first place.
Option C: While some minimal absorption might occur, the primary and lethal mechanism is suffocation, not systemic toxicity from diffusion. The effect is too rapid for diffusion to be the main cause.
Option D: Kerosene does not have a corrosive or burning effect on the larval body wall. The action is mechanical (suffocation), not chemical (burning).

Visual 1: Diagram showing an Anopheles larva breathing at the water surface and how an oil film blocks its spiracles.
Visual 2: Infographic comparing the breathing postures of Anopheles, Aedes, and Culex larvae to illustrate their vulnerability to surface films.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanism of action of larvicides (kerosene) in mosquito control as background academic context rather than a clinical decision trigger.
This knowledge is crucial for Community Health Nurses involved in vector-borne disease prevention programs, such as those for Malaria, Dengue, and Filariasis.
Nurses educate communities on source reduction (eliminating breeding sites) and simple larvicidal methods, emphasizing safety precautions.
A key nursing role is advising against the use of kerosene in drinking water sources or fish ponds due to its toxicity and environmental impact.

How to Approach the Question

Identify the core scientific question: How does kerosene, an oil, kill mosquito larvae in water?
Recall the basic biology of a mosquito larva: It lives in water but needs to breathe air from the atmosphere.
Consider the physics of oil and water: Oil is less dense and does not mix with water, so it will form a film on the surface.
Synthesize these two points: An oil film on the water surface will create a barrier between the aquatic larva and the atmospheric air it needs to breathe.
Evaluate the options based on this understanding. 'Prevention of spiracle to come in contact with air' perfectly describes this mechanism of suffocation.
Eliminate other options: 'Entry into tract', 'diffusion', and 'burning' describe different mechanisms (internal blockage, poisoning, chemical corrosion) that are less direct and not the primary mode of action for surface oils.

Concept Tested & Keywords

Concept Tested: Mechanism of action of larvicides (kerosene) in mosquito control.
Stem keywords: Spraying kerosene, stagnant water, kill Anopheles
Lead-in keywords: due to
Negative lead-in flag: false

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