Determinants ofAedesmosquito larval ecology in a heterogeneous urban environment- a longitudinal study in Bengaluru, India
Authors: Deepa D. , Rohini P.D. , Lakshmi M. Iswarya , Isvaran Kavita , Ghosh Susanta Kumar , Sutharsan G , Ishtiaq Farah 
Published: June 2023

Background

Aedes-borne disease risk is associated with contemporary urbanization practices where city developing structure function as a catalyst for creating mosquito breeding habitats. We lack better understanding on how the links between landscape ecology and urban geography contribute to the prevalence and abundance of mosquito and pathogen spread.

Methods

An outdoor longitudinal study in Bengaluru (Karnataka, India) was conducted between February 2021 and June 2022 to examine the effects of macrohabitat types on the diversity and distribution of larval habitats, mosquito species composition, and body size to quantify the risk of dengue outbreak in the landscape context.

Findings

A total of 8,717 container breeding sites were inspected, of these 1,316 were wet breeding habitats. A total of 1,619 mosquito larvae representing 16 species from six macrohabitats and nine microhabitats were collected.Aedes aegyptiandAe. albopictuswere the dominant species and significantly higher in artificial habitats than in natural habitats. Breeding preference ratio forAedesspecies was high in grinding stones and storage containers. TheAedesinfestation indices were higher than the WHO threshold and showed significant linear increase from Barren habitat to High dense areas. We foundAe. albopictusbreeding in sympatry withAe. aegyptihad shorter wing length.

Interpretation

The majority larval habitats were man-made artificial containers. Landscape ecology drives mosquito diversity and abundance even at a small spatial scale which could be affecting the localized outbreaks. Our findings showed that sampling strategies for mosquito surveillance must include urban environments with non-residential locations and dengue transmission reduction programmes should focus on ‘neighbourhood surveillance’ as well to prevent and control the rising threat ofAedes-borne diseases.

Funding

This research was financially supported by Tata Trusts funding to Tata Institute for Genetics and Society.

Research in context

Evidence before the study

The quality of mosquito larval habitats (breeding sites) is one of the most important determinants of the distribution and abundance of mosquito species. Cities offer a heterogeneous landscape with a gradient of temperature, vegetation, built infrastructure (piped water access, water storage) which can vary in microclimate at fine spatial scales. Entomological surveys are often biased towards locations or houses with high mosquito densities. Sampling strategies for mosquito surveillance must include urban environments with non-residential locations.

Added value of this study

Understanding the linkages between environmental conditions (e.g., hydrology, microclimate), land use, climate change, increasing urbanization are some of the key factors modulating the mosquito life-history traits which influence epidemiologically relevant behaviors and their ability to transmit diseases. Our longitudinal study shows that a combination of manmade larval habitats and landscape ecology drives mosquito diversity and abundance even at a small spatial scale which could be affecting the incipient disease outbreaks.

Implications of all the available evidence

From science to policy perspective, our study is first comprehensive study in Bengaluru, India which shows that sampling strategies for mosquito surveillance must include urban environments with non-residential locations. We demonstrate that dengue transmission reduction programmes should focus on ‘neighbourhood surveillance’ as well to prevent and control the rising threat ofAedes-borne diseases.