Larval Surveillance of Aedes Mosquito for Assessing Dengue Prevalence in South Zone, Delhi, India

Abstract

Introduction: Dengue is a rapidly spreading mosquito-borne viral disease, now affecting over half the world’s population, with South-East Asia bearing the highest burden. Transmitted mainly by Aedes aegypti, outbreaks peak after the monsoon due to abundant breeding sites in urban areas. Continuous vector surveillance and integrated mosquito management are essential, with larval surveys using House Index, Container Index, and Breteau Index as key indicators.

Method: In the present study, five wards from South Zone, Delhi, were selected, covering eight diverse localities including government institutions, high-income residential areas, urban villages, and slum settlements. A door-to-door entomological survey was conducted from January to December 2024, inspecting 60 houses per locality each month. Aedes larvae were identified in water-holding containers such as plastic containers, flower pots, coolers, metal containers, tyres, cement cisterns, water tanks, and others with breeding sites recorded and larval indices (HI, CI, BI) calculated.

Results: Monthly entomological surveillance in eight South Zone localities of Delhi (2024) covered 4,320 households and 7,289 containers, with 262 houses and 418 containers positive for Aedes breeding. The overall indices were HI: 6.1%, CI: 5.7%, and BI: 9.7. Seasonal trends showed the lowest values in December (HI: 0.8%, CI: 0.6%, BI: 0.8) and the highest in August (HI: 19.2%, CI: 16.9%, BI: 32.5). Indices rose gradually from March, peaked in July–August during monsoon, and declined by December, reflecting strong climatic influence on vector proliferation.

Conclusion: Larval surveillance in South Zone, Delhi, showed strong seasonality of Aedes aegypti breeding, peaking in July–August with highest HI, CI, and BI, indicating maximum dengue risk. Most breeding occurred in domestic containers, especially coolers, plastic containers, and water tanks. Findings stress upon integrated vector management (IVM) through continuous surveillance, source reduction, safe water storage, and community awareness.