# Bacterial community structure and diversity of common mosquito species in Chengdu: Insights from PacBio third-generation sequencing and public health implications

## TL;DR

This study maps mosquito-borne disease risks in Chengdu by analyzing the bacteria living in four mosquito species and how they vary across urban and rural areas.

## Contribution

The study provides the first comprehensive baseline dataset on mosquito-microbe interactions in Chengdu using PacBio sequencing and five years of ecological surveillance.

## Key findings

- Aedes albopictus had the highest diversity of unique symbiotic bacteria, including Wolbachia, which may suppress arboviruses.
- Rural outer-ring areas had 10-fold higher mosquito densities than urban centers, with distinct microbial clustering among species.
- Klebsiella variicola was found in high abundance in Armigeres subalbatus, a potential public health risk.

## Abstract

Mosquitoes, as critical vectors of diseases such as Japanese encephalitis, dengue fever, and yellow fever, pose significant public health risks in Chengdu, a subtropical city in southwestern China. The present study ecological surveillance and PacBio third-generation sequencing to characterize the symbiotic microbiota of four dominant mosquito species (Aedes albopictus, Culex pipiens quinquefasciatus, Culex tritaeniorhynchus, and Armigeres subalbatus) across urban and rural habitats. From 2020 to 2024, mosquito density monitoring revealed spatial heterogeneity(Aedes albopictus, Culex pipiens quinquefasciatus, Culex tritaeniorhynchus, and Anopheles sinensis), with outer ring areas exhibiting the highest density (34.69 mosquitoes per trap per night), while central urban zones had the lowest (3.60). Sequencing identified 717 high-quality Amplicon Sequence Variants (ASVs), with Aedes albopictus harboring the most unique bacterial species (191). Beta diversity analysis demonstrated distinct microbial clustering among species, driven by Pseudomonadota dominance (54.27–93.89%) and variations in secondary phyla (Bacteroidota, Campylobacterota). Functional prediction analysis via the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed significant disparities in the abundance of human disease-associated pathways across mosquito symbiotic microbiota (P = 0.049), with the disparities primarily observed in pathways related to bacterial, viral, and parasitic infections—categories of substantial public health relevance. Notably, Wolbachia (clade B) and Klebsiella variicola exhibited species-specific abundance patterns, underscoring their respective roles in potential pathogen suppression and public health risks. Unclassified taxa (norank_d__Bacteria, norank_p__Candidatus_Hydrogenedentes) clustered near novel mosquito-associated spirochetes, suggesting underexplored functional microbiota. This study establishes a foundational dataset for understanding mosquito-microbe interactions and inform the development of targeted strategies for mitigating vector-borne disease.

Mosquito-borne diseases like dengue and Japanese encephalitis disproportionately affect subtropical regions. Understanding how mosquitoes’ native microbes influence disease transmission remains a critical challenge, especially in under-resourced areas. Chengdu, a megacity in southwestern China, faces unique challenges due to rapid urbanization, climatic suitability for mosquito proliferation, and disparities in public health infrastructure compared to eastern coastal regions. This study integrates five years of ecological surveillance (2020–2024) and PacBio third-generation sequencing to map mosquito density patterns and characterize symbiotic bacterial communities in four dominant mosquito species (Aedes albopictus, Culex pipiens quinquefasciatus, Culex tritaeniorhynchus, and Armigeres subalbatus). Key findings reveal stark spatial heterogeneity in mosquito density, with rural outer-ring areas harboring 10-fold higher densities (34.69 mosquitoes per trap per night) than urban centers. Notably, Aedes albopictus exhibited the highest diversity of unique symbiotic bacteria (191 species), including Wolbachia (clade B), known to suppress arboviruses like dengue. Conversely, Armigeres subalbatus carried high abundances of Klebsiella variicola, an emerging human pathogen linked to severe infections. Functional annotation based on PICRUSt2 revealed significant species-specific variations in disease-related metabolic pathways within the mosquito symbiotic microbiota, with notable differences observed in the abundance of pathways associated with bacterial, viral, and parasitic infections. This work provides the first comprehensive baseline dataset on mosquito-microbe interactions in Chengdu, identifying actionable targets for biocontrol (e.g., leveraging Wolbachia) and facilitating the development of early-warning systems for pathogen surveillance. By bridging ecological, molecular, and public health perspectives, our findings offer critical insights for mitigating neglected tropical diseases in subtropical regions where socioeconomic disparities intersect with high disease burdens.