CE03 - Interactions Humains-Environnement

Discontinuities and Vector-Borne Diseases in Urban Areas. A Simulation Model of a Complex Pathogenic System. – MO3

MO3

Discontinuities and Vector-Borne Diseases in Urban Areas. A Simulation Model of a Complex Pathogenic System.

Spatial simulation and epidemiology

MO3 aims (i) to develop a simulation model to study the sensitivity of epidemic dynamics to targeted anti-vector control scenarios and (ii) to evaluate in a large metropolis where dengue is endemic, Bangkok ( Thailand), the effectiveness of these strategies.

The MO3 project will be based on a model based on differential equations and multi-agent systems, with high spatial and temporal resolution, allowing a detailed description of the urbanized space and the variety of dynamics that unfold there, those of the vectors. and human populations. Vector dynamics will be influenced by the spatial and temporal heterogeneity of their ecological niche, those of humans by their daily mobility, linked in part to their place of residence, their socio-economic profile and their age. The calibration of the model will be based on various data: satellite images, censuses, social networks, retrospective vector and epidemiological data. We are also planning field surveys. Sites will be selected according to a gradient of the value of the ecological niche of the vector and a gradient of the value of the centrality of the places. Weekly surveys, over a period of 2 years, will make it possible to analyze the evolution of adult mosquito stocks with regard to these two indicators, and epidemiological surveys on populations at risk will make it possible to assess exposure levels, according to the same criteria. All of this data will also be used to calibrate and validate the simulation model. Exploration methods based on evolutionary algorithms will be used to evaluate, compare and prioritize the mechanisms of the model with regard to the simulated dynamics and the observations that they can or must produce or reproduce. These methods will also evaluate and compare vector control strategies against the epidemiological dynamics simulated by the model, in search of the most effective strategy or strategies. The ambition of MO3 is therefore to develop a generic method which makes it possible to carry out anti-vector struggles in priority areas, thus allowing local actors to optimally allocate their available, but limited, resources.

1. Meta-analysis of the work relating different risk indicators (presence of potential breeding sites, positive breeding sites for the larvae, mosquito adults, incidence rate) with socio-economic and cultural factors (social category, KAP study, income etc.): In the process of being finalized, a publication in preparation (thesis by Antoine Longo, UMR IDEES).
2. Design and development of an agent model to explore the role of human mobility and differentiated mosquito densities in the propagation of a virus (NetLogo model): Exploration phase and model sensitivity analysis (post -doc of Hélène Arduin, UMR IDEES).
3. Design of the conceptual framework of the MO3 model (Scala model): In progress (post-doc by Hélène Arduin, UMR IDEES, ISC-PIF)
4. Design of a system allowing the detection of egg-laying sites in an urban environment in photos taken from Google Street View (Yolo v5 model): In progress, the system has been validated on a type of breeding site present in IdF (internship in collaboration with the LITIS IT laboratory, Rouen).
5. Design of a statistical processing chain to estimate air temperatures from satellite images (R script): In progress (IDEES internship)
6. Identification of the type of breeding grounds of the tiger mosquito and analysis of the socio-spatial determinants of its abundance in Ile-de-France: Field surveys with agents responsible for vector surveillance and data collection have enabled to establish a typology of the lodgings present in the area (IDEES internship in collaboration with the Entente de la Lutte Inter-Départementale contre les Zoonoses, IdF).
7. Analysis of dengue seroprevalence data from a cohort of 400 children in Bangkok, retrospective study: carried out (University of Chulalongkorn, Institut Pasteur).
8. Construction of centrality and mobility indicators in Bangkok: In finalization (IDEES)

The pandemic seriously impacted the project schedule. On the one hand, the planning and carrying out of the data collection in Bangkok in partnership with our colleagues from Chulalongkorn University, initially planned to start in 2021, had to be postponed and postponed by one year, in 2022 ( WP3 task 3). This delay should not impact our schedule given the postponement automatically granted by the agency. Despite everything, we remain dependent on sanitary conditions in Thailand where our partners are currently 100% involved in the management of the pandemic. On the other hand, we experienced human resources issues during this difficult period which led to a certain delay in relation to the initial schedule, in particular on WP2, resulting in a postponement of activities on WP3 task 4. A reorganization of operations between the various partners should allow us to achieve the set objectives on time

1. Cebeillac A., Daudé É. (à paraître), Mobilité quotidienne et diffusion des épidémies, in. Vallée J (ed.), Géographie de la santé et mobilité, ISTE-WILEY.
2. Longo A., Daudé É., Paul R. (2021), Évaluation des zones et périodes potentiellement favorables à l'implantation, à la prolifération et au maintien de population de moustiques vecteurs de la dengue, du virus Zika et du Chikungunya en région parisienne et à Bangkok (Thaïlande), Rencontres Géographie de la santé, 4-5/02/2021, Rennes.

Vector-borne diseases (dengue, Zika, chikungunya) are an important public health issue. Understanding their transmission dynamics remains a major challenge at the sub-urban level. Indeed, environmental heterogeneities, variations in vector densities and daily mobility constitute a lock on the definition of epidemic risk indicators at this scale. MO3 therefore aims to (i) develop a simulation model to study the sensitivity of epidemic dynamics to targeted scenarios of anti-vector fights and (ii) evaluate in a large metropolis where dengue is endemic, Bangkok (Thailand), the effectiveness of these strategies.
In cities where these diseases are endemic, our first hypothesis is that the urban territory has a limited number of places favorable to the maintenance of mosquito population during the inter-epidemic season, sufficient to ensure local, continuous and low-noise circulation of viruses. With seasonal changes (rising temperatures, monsoon rains), vector populations are exploding, increasing the risk of spreading viruses from these areas. Our second hypothesis is that the structuring of urban space (residence, economic and commercial activities, vegetated spaces) and the resulting discontinuities structure the daily mobilities of populations, and potentially the spread of pathogens in epidemic proportions. It is therefore essential to identify these potential reservoirs of pathogen diffusion early. Moreover, in cities where these diseases are not endemic, or not yet present, the dynamic mapping of the environmental risk based on the ecology of the mosquito must make it possible to identify and monitor the places and the periods favorable to the implantation and the proliferation of mosquito vectors.
To achieve these objectives, the MO3 project will rely on differential equations and agent-based model, with high spatial and temporal resolution, to describe finely the urbanized space and the variety of dynamics that unfold there, those of vectors and human populations. Vector dynamics will be influenced by the spatial and temporal heterogeneity of their ecological niche, those of humans by their daily mobility, partly linked to their place of residence, their socio-economic profile and their age. The calibration of the model will be based on various data: satellite images, census, social networks, vector and epidemiological retrospective data. We also plan field surveys. Sites will be selected according to a value gradient of the ecological niche of the vector and a value gradient of centrality of the places. Weekly surveys over a 2-year period will be used to analyze the evolution of adult mosquito stocks with respect to these two indicators, and epidemiological surveys of at-risk populations will be used to assess exposure levels, according to these two indicators. All of this data will also be used to calibrate and validate the simulation model. Exploration methods based on evolutionary algorithms will be mobilized to evaluate, compare and hierarchize the mechanisms of the model with regard to simulated dynamics and observations that they can or must produce or reproduce. These methods will also evaluate and compare vector control strategies against the epidemiological dynamics simulated by the model, in search of the most effective strategy or strategies. MO3's ambition is therefore to develop a generic method that allows for vector-based struggles in priority areas, thus enabling local actors to optimally allocate their available but limited resources.

Project coordination

Christophe Imbert (IDENTITE ET DIFFERENCIATION DE L'ESPACE, DE L'ENVIRONNEMENT ET DES SOCIETES)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

INSTITUT PASTEUR
ISC-PIF Institut des Systèmes Complexes - Paris Ile de France
IDEES IDENTITE ET DIFFERENCIATION DE L'ESPACE, DE L'ENVIRONNEMENT ET DES SOCIETES

Help of the ANR 576,369 euros
Beginning and duration of the scientific project: October 2019 - 48 Months

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