Spatial Epidemiology

Objectives

The programme “Spatial Epidemiology: Emergence and Control of Transmissible Diseases in South India” is devoted to the study of the causes of the emergence and/or re-emergence of the arboviruses (dengue, West Nile, Japanese encephalitis) and parasitic and bacterial diseases (filariasis, malaria, leptospirosis) from a multidisciplinary point of view. Research bearing on the relations between human health, the bio-ecology of vectors and the environment is pursued from two perspectives and is carried out in two localities:

1. a retrospective study of the effects of urbanization on the epidemiology of vector-borne diseases in Puducherry (Pondicherry) over the last thirty years,

2. an analytical spatial study of the dynamics of the transmission of diseases in the megapolis of Chennai (Madras).

The aim of the research programme is to show the links between urbanization and the epidemiology of transmissible diseases. Together with an analysis of the seasonality of incidence, this would make it possible to develop an early warning system that could be used locally by those responsible for health policies.

The research team studies in particular:

• the temporal and spatial evolution of foci of contact and of cycles in the rural, peri-urban and urban zones
• the seasonality of certain risk factors due to climate and human migrations
• the environmental conditions and their modifications that govern the development of the vectors and animal reservoirs involved in the endemicization and/or epidemicization of diseases
• the level of risk of transmission, characterized by a combination of factors connected with the abiotic (infrastructures, milieux and landscapes) and biotic (abundance of vectors, intensity of contacts with humans or animals) environment and linked to health (immunity level of the populations, pathogenicity of different strains of infectious agents, health care systems) and to urban development (water storage, soil management, migrations, type of settlement).

Materials and Methods

Selection of sentinel areas

The data pertain to geography (both descriptive and human), to bio-geography (spatial distribution of animal species), biology and ecology (vectors and hosts). The analysis of these data takes the environment and its evolution into particular account.

Zones of study

The method of selection in Chennai is based on a preliminary stratification of the city according to the degree of urbanization and socio-economic indicators. Sentinel zones reflect the diverse ecosystems including, for example, urban sub-spaces or characteristic rural landscapes.

In Puducherry, studies are based on all zones that have been confronted with urban evolution in the course of the last thirty years.

The analysis of satellite images will provide a detailed outline of the physical environment of the zones under study and of its temporal evolution.

Collection of data

The use of questionnaires for households and serological surveys in the rural, peri-urban and urban sentinel zones (follow up of cohorts at regular intervals of time) Extensive study of the medical care centres present in each zone (provision of medical care, health problems connected with water or waste in the agglomerations, etc.).

Sampling and identification of insect vectors and their parasites.

Analysis of public health statistics and, more particularly in Puducherry, of existing documents (scientific publications, annual reports, theses, etc.) at the concerned departments (Health and Family Welfare, Municipal Administration and Water Supply, Public Works, Housing and Urban Development, Agriculture, Animal Husbandry and Fisheries, India Meteorological Department, Corporations of Chennai and Puducherry, etc.).

Partners

• VCRC: Vector Control Research Centre, Puducherry (MoU in progress)
• IRD: Institut de Recherche pour le Développement Paris (agreement)
• Corporation of Chennai (MoU)

Team

Download research abstracts (.pdf) and an outline of the Chennai Project (.pdf)

Head of project

• Dr. Bernard Mondet, entomologist, researcher at the Institut de Recherche pour le Développement (IRD), UR 178, “Fundamentals and Domains of Disease Emergence”, affiliated with the IFP.

Associated researchers

• Dr. P.K. Das, Director, Population Science, Modelling and Bio-Informatics (VCRC)
• Dr. R. Ravi, Deputy Director (S.G.), Applied Field Research (VCRC)
• Dr. P. Jambulingam, Deputy Director, Vector Biology and Control (VCRC)
• Dr. S. Sabesan, Deputy Director, Applied Field Research (VCRC)
• Dr. S.L. Hoti, Assistant Director, Product Development (VCRC)
• Dr. G. Rajendran, Senior Research Officer, Applied Field Research (VCRC)

Doctorates and Post Doctorates

• Sanjeevi Prasad, Loyola University, Chennai
• Patrick Sakdapolrak, Bohne University, Germany
• Thomas Seyler, doctorant en Géographie de la Santé, Université de Paris X, fellowship de l’European Centre of Diseases Control (ECDC).

Funding

• IRD: UR 178 “Conditions and Territories of the Emergence of Diseases”
• French Institute of Pondicherry, Puducherry
• Vector Control Research Centre, Puducherry

Expected Results

• Production of maps showing the risk of infection, localization of zones where pathologies are concurrent – or mutually exclusive
• Identification of risks and of their spatio-temporal combination. Representation of the links between the urbanization process and the distribution of diseases in a metropolis
• Co-edited scientific publications (IFP and VCRC-IMCR) Development of a thorough epidemiological model for the creation of an early warning system.