# Vector Control Methods

> Vector control for FMGE PSM: source reduction, larvivorous fish, IRS insecticides, LLINs, Aedes indices thresholds and integrated vector management.

- Canonical URL: https://prepelephant.com/topics/fmge/community-medicine/vector-control-methods-fmge
- Exam / course: FMGE · Subject: Community Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Vector Control Methods", PrepElephant, https://prepelephant.com/topics/fmge/community-medicine/vector-control-methods-fmge

## Direct answer

Source reduction beats spraying wherever water can be denied to mosquitoes — that principle organises every vector control method worth listing. Anti-larval measures work before the bite: environmental source reduction (filling, draining, weekly emptying of Aedes containers), biological control with larvivorous fish (Gambusia and Poecilia) and bacterial biolarvicides (Bacillus thuringiensis israelensis), plus chemical larvicides such as temephos. Anti-adult measures cut the adult population: indoor residual spraying with synthetic pyrethroids at roughly 25 mg per square metre (DDT now restricted to kala-azar-endemic districts at 1 g per square metre), long-lasting insecticidal nets, and thermal fogging with pyrethrum for outbreak response. Personal protection adds repellents (DEET, IR3535), screens and treated clothing; legislation underpins it all — municipal bylaws penalising Aedes breeding and Indian Penal Code sections 269-270 on acts likely to spread infectious disease.

## What you must remember

- **The Aedes indices:** house index (percentage of houses positive for larvae) critical above 10 per cent; container index (percentage of wet containers positive) critical above 20; Breteau index (positive containers per 100 houses) critical above 5.
- **Anti-larval trio:** environmental (source reduction, water management, mosquito-proofing of tanks), biological (larvivorous fish Gambusia affinis and Poecilia reticulata; Bti and Bacillus sphaericus), chemical (temephos in potable-water containers, mineral oils and Paris green historically).
- **IRS specifics:** synthetic pyrethroids such as deltamethrin (about 25 mg per square metre) for malaria; DDT restricted to kala-azar-endemic districts (Bihar, Jharkhand, West Bengal and eastern Uttar Pradesh); two rounds a year in endemic areas.
- **Space spray:** two per cent pyrethrum extract thermal fogging — immediate knockdown without residual effect — for dengue outbreak response, combined with source reduction, never substituted by it.
- **Personal protection:** DEET, IR3535 and picaridin repellents; long-lasting insecticidal nets (deltamethrin-incorporated, effective about three years); screens, coils and vaporisers; protective clothing for outdoor and forest workers.
- **Vector-specific logic:** Aedes is a day-biting domestic container breeder — fogging plus source reduction, not IRS; Anopheles rests indoors after night biting — IRS and nets work; Culex quinquefasciatus (filariasis) breeds in organic water — sanitation and drainage; Japanese encephalitis vectors breed in rice paddies — alternate wetting-drying and cattle-shed spraying.
- **Legislative tools:** municipal bylaws on domestic breeding checks; IPC 269/270 for negligent or malignant acts likely to spread infection.
- **Integrated vector management (WHO):** evidence-based, locally adapted combination of methods with insecticide-resistance management (rotating insecticide classes), community participation and intersectoral action — the framework answer when the exam asks for "strategy" rather than a method.

## Choosing methods for one district's three problems

A district officer faces malaria in forest-fringe villages, dengue in the town, and Japanese encephalitis in rice-belt blocks. For malaria villages she orders LLIN distribution and IRS rounds timed before the monsoon peak, because Anopheles bites and rests indoors at night. For the town, the team runs Breteau index surveys ward by ward, serves notices under civic bylaws on tyre shops and construction sites, organises weekly dry days when every household empties and scrubs its water storage, and reserves fogging for the epidemic season — attacking larvae, since adult Aedes rest in dark corners where house spraying misses them. For the JE belt, the response is paddy water management with the agriculture department, larviciding of irrigation channels, shifting piggeries away from homes and child vaccination — because no house-spray reaches a rice-field vector. Three diseases, three ecologies, one IVM logic: match the method to the bionomics.

## Where students slip

Index thresholds are the numerical trap — Breteau 5, house 10, container 20 — and candidates swap them freely; anchor Breteau (containers per 100 houses) to 5, the smallest number with the biggest name. Second, DDT is not banned outright in India; its public-health use survives only for kala-azar vector control — "DDT is completely banned" is the planted false statement. Third, fogging is a measure of epidemic response, not routine Aedes control; routine control is source reduction, and exams frame exactly this hierarchy. Fourth, biological control names: Gambusia and Poecilia are fish, Bti is a bacterium — a matching question mixes all three with temephos, the chemical.

## Frequently asked questions

### What are the critical values of the Aedes larval indices?
House index above 10 per cent, container index above 20 per cent and Breteau index above 5 signal dengue transmission risk and trigger control action.

### Which larvivorous fish are used in biological control?
Gambusia affinis and Poecilia reticulata, released into wells, ponds and tanks where they consume mosquito larvae.

### What is indoor residual spraying and with which insecticides?
Coating interior walls and roofs with residual insecticide so resting mosquitoes pick up a lethal dose — synthetic pyrethroids such as deltamethrin for malaria, with DDT now restricted to kala-azar districts.

### Why is fogging alone insufficient for dengue control?
Thermal fogging kills only the adults present at that moment with no residual effect, while Aedes larvae keep emerging from containers — source reduction is the decisive, sustainable measure.

### What is integrated vector management?
A WHO strategy rationalising vector control by combining environmental, biological, chemical and personal-protection methods with resistance management, community participation and intersectoral action.