Sewage-driven mosquito proliferation in Urban India: a molecular and environmental correlation study in Coimbatore

Rapid urbanization and poor sewage infrastructure are intensifying mosquito breeding in Indian cities, heightening the risk of vector-borne diseases. This study investigates the relationship between sewage-contaminated environments and mosquito proliferation across four urban sites in Coimbatore, Tamil Nadu. Entomological indices-House Index (HI 24.7-31.8%), Container Index (CI 28.5-38.1%), and Breteau Index (BI 34.2-46.7%)-revealed high larval prevalence. Water bodies in polluted areas exhibited critical quality degradation, including elevated biological oxygen demand (BOD up to 12.6 mg/L) and low dissolved oxygen (DO as low as 1.2 mg/L). Molecular identification using polymerase chain reaction (PCR) confirmed the dominance of Culex quinquefasciatus and Aedes aegypti. Statistical analysis showed strong correlations between larval density and water quality parameters (e.g., r = 0.82 for BOD, r = -0.76 for DO). Larval density was negligible in treated wastewater zones, highlighting the protective role of proper sanitation. Although the study is limited to pre- and post-monsoon sampling within Coimbatore, the findings offer actionable insights for integrated vector management (IVM) and GIS-based surveillance strategies to guide urban mosquito control policies.