We initially worked with three primary data inputs: a geoJSON and Neighborhood Shapefile from LA Times, as well as a JSON file from Calsurv. After converting, cleaning, and merging the data, we generated four files. These files served as the basis for four main visuals: a 3D space-time cube, a Tableau interactive map, a dot density map, and a heat map. Each visualization was carefully selected to enhance public understanding of the spread of Aedes mosquitoes.
While choropleth maps have traditionally been used for public education, we found them inadequate for representing and communicating the data effectively. Therefore, our chosen visualizations and analysis provide greater ease of comprehension and reduce potential confusion. Our data covers an eight-year timeframe (2011-2019), and we explored how to incorporate time into our analysis.
Instead of relying on side-by-side snapshots, which can isolate events, we utilized a 3D space-time cube to showcase both spatial and temporal relationships. This approach involved aggregating points into space-time bins, counting the number of points, and calculating optional statistics for attributes. We divided our data into a fishnet grid of 17 time steps with six-month intervals. The entire time period covered by the space-time cube spans 102 months. We aggregated a total of 1,818 points into 529 fishnet grid locations, with each location measuring 4,844 meters by 4,844 meters.
The Tableau interactive map and heat map were utilized to help users better understand density and hotspots. Additionally, we employed a dot density map to represent the total Aedes detections, highlighting the distinctive spatial separation between the two species.
Although Aedes albopictus was established in Los Angeles County in 2011, three years prior to the arrival of Aedes aegypti, aegypti has emerged as the dominant species in terms of population size and spread. The summary analysis generated by the space-time cube revealed an overall growth increase over time for Aedes aegypti, with a p-value of 0.0651. Conversely, Ae. albopictus displayed a decreasing trend over time, with a p-value of 0.0834. This distribution and count can be attributed to competition between the species.
Competitive interactions between Aedes aegypti and Ae. albopictus play a critical role in shaping life history traits and population characteristics. The overlapping resource requirements and similarities in life history strategies provide a basis for these competitive interactions. The study conducted by Banerjee et al. emphasizes the influence of larval habitat food quality on the outcome of competition between the two species. It reveals that Ae. albopictus develops faster but achieves a smaller size compared to Ae. aegypti under interspecific competition conditions. The dominance of one species over the other may also be influenced by variations in resource utilization patterns in larval habitats (Banerjee et al., 2017).
Reference: Banerjee, S., Mohan, S., Pramanik, S., Banerjee, S., Saha, G. K., & Aditya, G. (2017). Effect of food types on competitive interaction between Aedes aegypti (LINNAEUS, 1762) and Ae. albopictus (SKUSE, 1894) (Diptera, Culicidae): a proximate level appraisal, Polish Journal of Entomology, 86(2), 99-118. doi: https://doi.org/10.1515/pjen-2017-0008
Click here for an interactive map of Los Angeles County displaying Aedes detections over time.
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