What influence do socio-ecological factors have on mosquito density?

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A new study has investigated the influence of socioeconomic factors on the density of Tiger mosquitoes in Baltimore, MD, USA, discovering that environmental disparity may leave low-income residents more vulnerable to mosquito-borne diseases.

The article, published recently in the Journal of Medical Entemology, aimed to examine the interactions of socio-ecological processes with abiotic drivers of mosquito populations, including the roles of infrastructure and vegetation within neighbourhoods.

Author Shannon LaDeau, from the Cary Institute of Ecosystem Studies (NY, USA), explained:  “We are interested in how land cover, microclimate and socioeconomics influence the distribution of tiger mosquitoes. In Baltimore and other temperate cities, the interplay of these factors determines when and where mosquitoes emerge and the extent to which they pose a risk to people.”

The researchers monitored mosquito activity over 3 years in five west Baltimore neighborhoods – study sites spanned neighborhoods with low, medium and high socioeconomic status. The team carried out block-scale surveillance of mosquito breeding habits three times during each mosquito season; in addition, adult mosquitoes were sampled every 3 weeks from May–September.

To investigate the influence of landscape features on mosquito prevalence, the group mapped neighborhoods using block-by-block surveys and satellite imagery. Utilizing a hierarchical statistical modeling approach they then assessed environmental and climatic influence, discovering that decaying infrastructure and vegetation are important determinants of mosquito populations.

The researchers reported that areas with a lower socioeconomic status saw higher levels of mosquitoes due to an increased proportion of vacant lots and abandoned building sites, which provided breeding sites for the insects.

However, the group observed that this correlation not static; when precipitation was low, mosquitoes were more likely to be found in higher-income neighborhoods owing to a managed habitat. LaDeau explained: “In a city like Baltimore, hot, dry conditions should cause mosquito populations to decline. Instead, in higher income neighborhoods, residents water their yards and enable mosquito populations to survive. That said, overall, our surveys found much larger mosquito populations in lower income neighborhoods.”

The team argue that this study highlight a need for fine spatial-scale modeling of mosquito habitat in order to ensure more accurately target vector control.

Lead author Eliza Little (Columbia University, NY, USA) concluded: “This study highlights the dual needs for personalized mosquito control on a lot-by-lot basis and public education across different socioeconomic neighborhoods to implement effective control strategies. Our work can also inform urban greening strategies. There can be unintended consequences when green spaces are added to cities without first removing mosquito-sustaining containers.”

Sources: Little E, Biehler D, Leisnham PT, Jordan R,Wilson S & LaDeau SL. Socio-Ecological Mechanisms Supporting High Densities of Aedes albopictus (Diptera: Culicidae) in Baltimore, MD. J Med Entomol. doi:10.1093/jme/tjx103 (2017) (Epub ahead of print); www.eurekalert.org/pub_releases/2017-06/cioe-iub063017.php

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