BZZZZZzzzZZZ Oh No Mosquito! Urban Vector-Borne Disease Ecology

It is definitely that time of year again: insects and other invertebrates seem to spawn from every nook and cranny. We see snails feasting on freshly emerged leaves, earthworms being snatched away by hungry and breeding birds and flies scouting for a place to lay their eggs. We double-check for ticks after a nice forest walk and start closing windows to keep those annoying mosquitoes out of our bedrooms at night. Clearly, it is not so strange that we encounter them everywhere: their wide spread in urban environments enables close and frequent contact to humans.

These terrestrial invertebrates are present in basically all urban ecosystems. While they serve crucial roles in the circulation of energy sources and material flow, they pose a significant threat to the zoonotic transmission of human pathogens and increased disease risks. Rapid urbanization and approaching global warming challenges influence these invertebrate populations. This causes a ripple effect increasing the risk on public health.¹ Here, we explore the urban vector-borne disease ecology of mosquitoes especially, through insights from recent research by Kache (2020), Wilke (2021) and Newman (2023). Also, we describe the Urban One Health perspectives proposed as potential solution in Ellwanger et al. (2022).

Mosquitoes Thrive in Urbanized Areas

Mosquitoes are well known human disease vectors. Anopheles and Aedes (aegypti) are infamous for their transmission of malaria, dengue, yellow fever, chikungunya and Zika viruses.² They feed on humans and lay their eggs in water containers found in human-dominated areas. Mosquito-borne diseases are a threat to urban ecosystems because of the lower species diversity found there, which provides niches low in predators. Additionally, microclimates and the high human population density and in urbanized areas makes them well suited for viral and mosquito development. The population often grows faster than the available infrastructure in cities with limited resources and unregulated housing. This makes it hard to provide public services fairly, and can lead to higher risks of disease in warmer regions.

City Structures

Cities consist of all sorts of hierarchically structured pieces of land for different purposes. The patchwork of vegetation, buildings and infrastructure affects virus and vector traits like replication and development. Kache et al. describe that the composition of the patches determines the risk; and the configuration and connections between them determines the disease spread.³ Furthermore, it has been established that storm drains harbour Aedes species in the collected rainwater. And in addition, water storage habits, piped water access and even certain high-producing households all shape local mosquito populations.

Human Effects

Because mosquitoes typically do not fly very far, scientists have linked human movement to Aedes-borne virus introduction into neighbourhoods. This also leads to continued circulation within cities.³ Finally, it gets increasingly complex when human social structures are added to the mix.³ People and places change over time in their relationship to each other. This influences behaviour and environment and thus further influences urban patterns affecting mosquito-borne disease risk. The prevalence of mosquito-borne diseases, especially by Aedes species is increasing worldwide and is at least partially related to urbanisation. Kache et al end by summarizing that while risks are different between cities, integrating landscape ecology, urban geography and complex adaptive systems could improve our understanding of Aedes-borne disease. An overview of the urban system properties determining Aedes-borne disease is shown below (Fig.1).³

 

Experimental Research on Water Sources and Abundance Patterns

Different researchers have performed experimental studies to show how urban environments, especially water structures, shape abundance patterns. Wilke et al (2021) demonstrate that abundance of mosquito disease-vectors Aedes aegypti and Culex quinquefasciatus in Miami-Dade, Florida increased while overall species richness declined in urban areas. The key factors identified were resource availability and human-related water sources, as they observed completely distinct mosquito community composition, richness and abundance unrelated to geographic proximity of the traps, but related to e.g. rain-flooded habitats.⁴

Similarly, Newman et al.(2024) describe how water structures drive abundance patterns. In urban, dry regions like Maricopa County, Arizona, the abundance of Aedes aegypti mosquitoes is influenced by both natural and anthropogenic water sources. While precipitation plays a role, its impact is quite complex. The authors show that rain during critical developmental periods for mosquitoes can suppress abundance. Specifically, precipitation two days before trapping, negatively correlated with mosquito presence, likely due to interference with larval development or emergence. Nevertheless, anthropogenic water sources like stormwater drains, ornamental features, and landscape irrigation, provide important breeding habitats for mosquitoes during long dry spells. Actually, 28% of traps with female mosquitoes contained individuals during periods with minimal precipitation, indicating reliance on anthropogenic water sources.⁵ This stresses the need to further investigate these complex patterns. Also, this emphasizes the importance of urban water management in controlling mosquito populations and reducing disease transmission risks.

Implications for Urban Health and Planning

Thinking of mosquitoes as just annoying pests buzzing in your ear at night overlooks their role in a complex global problem: one that is becoming increasingly urgent with rising environmental challenges. Additionally, researchers must examine how social inequalities, like limited access to healthcare, housing, and education, drive the pivotal challenge of vector-borne diseases in cities. Integrative strategies linking public health, ecology and urban planning are necessary. The One Health approach, which combines human, animal and environmental health, could be essential for this.⁶

Finally, published research, like discussed above, shows that badly managed water systems create the breeding grounds essential to this problem. Thus, urban planners should design environments limiting vector habitats, for example by supporting biodiversity and ecological resilience. Nevertheless, long-term solutions must also address broader structural issues, accounting for societal inequality and the burden on marginalized communities. This requires fair investment in water management, inclusive urban design, and policies that promote environmental stewardship.⁶ After all, public health is a community effort and keeping the (infectious) buzz away starts with all of us.

 

References

1. Xie A, Zhang Y, Breed MF, An X, Yao H, Huang Q, Su J, Sun X. Terrestrial invertebrate hosts of human pathogens in urban ecosystems. Eco Environ Health. 2024 Apr 16;3(3):369-380. doi: 10.1016/j.eehl.2024.04.003. PMID: 39281069; PMCID: PMC11399638.
2. European Centre for Disease Prevention and Control. (n.d.). Aedes aegypti – Epidemiology. Retrieved May 8, 2025, from https://www.ecdc.europa.eu/en/disease-vectors/facts/mosquito-factsheets/aedes-aegypti#Epidemiology
3. Kache, P.A., Santos-Vega, M., Stewart-Ibarra, A.M. et al.Bridging landscape ecology and urban science to respond to the rising threat of mosquito-borne diseases. Nat Ecol Evol 6, 1601–1616 (2022). https://doi.org/10.1038/s41559-022-01876-y
4. Wilke, A.B.B., Vasquez, C., Carvajal, A. et al.Urbanization favors the proliferation of Aedes aegypti and Culex quinquefasciatus in urban areas of Miami-Dade County, Florida. Sci Rep 11, 22989 (2021). https://doi.org/10.1038/s41598-021-02061-0
5. Newman, E.A., Feng, X., Onland, J.D. et al.Defining the roles of local precipitation and anthropogenic water sources in driving the abundance of Aedes aegypti, an emerging disease vector in urban, arid landscapes. Sci Rep 14, 2058 (2024). https://doi.org/10.1038/s41598-023-50346-3
6. Ellwanger JH, Byrne LB, Chies JAB. Examining the paradox of urban disease ecology by linking the perspectives of Urban One Health and Ecology with Cities. Urban Ecosyst. 2022;25(6):1735-1744. doi: 10.1007/s11252-022-01260-5. Epub 2022 Jul 15. PMID: 35855439; PMCID: PMC9283848.

Featured Image Credit: Aedes aegypti mosquito feeding on a human - https://www.cdc.gov/dengue/transmission/index.html