Seasonal dynamics and environmental drivers of <i>Aedes aegypti</i> and <i>Aedes albopictus</i> (Diptera: Culicidae) in urban Punjab, Pakistan: evidence from larval surveillance

Aedes aegypti (L.) and Aedes albopictus (Skuse) are the primary vectors of dengue, and understanding their abundance, breeding habitat preferences, and environmental drivers is critical for effective surveillance in endemic regions of Pakistan. A larval surveillance study was conducted across 4 major cities in Punjab, Pakistan (Faisalabad, Lahore, Rawalpindi, and Multan) from 2023 to 2024, focusing on immature stages sampled from various indoor and outdoor containers. Indoor habitats accounted for 53.7% of positive sites, with bath tanks, evaporative coolers, water storage, and discarded tires being the most productive. Outdoor habitats, particularly tube wells and construction sites, accounted for a higher proportion of positive sites in Multan than in the other cities. A. aegypti was the dominant species in all 4 cities; however, the relative contribution of A. albopictus was higher in Rawalpindi and Multan than in Lahore and Faisalabad. The House Index (HI), Container Index, and Breteau Index (BI) exceeded World Health Organization transmission thresholds in Lahore and Faisalabad, with HI and BI being the most significant indicators of infestation, while Rawalpindi and Multan showed lower infestation levels. Seasonal effects were strong, with peak abundance during the monsoon (June to September) and post-monsoon (October to November) periods, coinciding with increased rainfall and humidity. Both species showed significant positive associations with rainfall and relative humidity; however, A. aegypti abundance was more strongly influenced by temperature, whereas A. albopictus was more strongly associated with rainfall and humidity. Community ordination revealed minimal differentiation between cities but significant seasonal shifts in composition. These findings indicate that monsoon-driven climatic conditions are key drivers of Aedes population dynamics in Punjab and highlight the need for intensified, seasonally targeted vector control. Control efforts should prioritize source reduction in highly productive domestic containers and locally important outdoor habitats, particularly before and during the monsoon and extending into the post-monsoon period to reduce dengue transmission risk.