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Accueil du site → Doctorat → Royaume-Uni → 2019 → Geospatial analysis of environmental risk factors of leptospirosis in East Africa. A multiscale, mixed method approach in spatial epidemiology

University of Glasgow (2019)

Geospatial analysis of environmental risk factors of leptospirosis in East Africa. A multiscale, mixed method approach in spatial epidemiology

Uzzell, Christopher

Titre : Geospatial analysis of environmental risk factors of leptospirosis in East Africa. A multiscale, mixed method approach in spatial epidemiology.

Auteur : Uzzell, Christopher

Université de soutenance : University of Glasgow

Grade : Doctor of Philosophy (PhD) 2019

Résumé partiel _ Leptospirosis is one of the most widespread, but neglected, zoonoses in the world. The disease is caused by infection with pathogenic Leptospira species spread by the urine of mammalian hosts. It is an acute febrile illness with a wide variety of clinical manifestations and, in recent years, has come to international attention as a major re-emerging infectious disease. Leptospirosis has a broad, almost ubiquitous, geographic distribution. However, the highest incidence of leptospirosis is observed throughout tropical, low- and middle-income regions of the world where the disease is considered a major cause of non-malarial febrile illness, especially throughout rural environments. Leptospirosis is considered endemic across East Africa, however, due to a scarcity of robust data on leptospirosis occurrence in humans or animals, awareness of the illness is relatively low and there are few disease burden estimates from the region. As such, the current status of leptospirosis in East Africa remains largely unknown. Effective targeting of leptospirosis control strategies throughout areas thought to experience a high burden of infection rely on detailed and accurate understanding of the geographical and temporal distribution of disease, the population at risk and the intensity of disease transmission. Such information can be generated using spatially explicit geostatistical methods which explore linkages between the distribution and intensity of leptospirosis occurrence and environmental risk factors known, or hypothesised, to have an influence on the distribution of the disease. The spread of the Leptospira bacteria relies on the abundance and geographic distribution of suitable animal maintenance hosts, such as rodents and livestock. Once shed into the environment, the survival of the bacteria is linked to a suite of climate, hydrological and terrestrial environmental processes. In general, the prevailing environmental conditions in East Africa are favourable for active transmission of Leptospira. However, significant knowledge gaps remain in relation to the specific epidemiology and environmental determinants of infection risk across the region at broad and local scales. In that context, the objective of this thesis is to examine the spatiotemporal patterns of human and animal exposure to leptospirosis in urban and rural communities of East Africa and explore potential environmental drivers of infection. To achieve this objective, and to extract maximal value from limited data availability, a novel mixed method approach in GIS-based spatial epidemiology was devised. Three distinct bodies of evidence-based research relevant to the spatial epidemiological characteristics of leptospirosis were carried out. Crucially, both data- and knowledge-driven methodological approaches were implemented in context specific case studies of investigation. Firstly, data from a geospatially explicit longitudinal study were used to determine the fine scale environmental covariates of leptospirosis within a canine sample population in a small informal settlement located in Nairobi, Kenya. High spatial resolution remotely sensed datasets and serological data were coupled within a multilevel mixed effect geostatistical modelling approach to examine environmental risk factors and generate hypotheses concerning the likely sources and transmission pathways of infection in dogs. Highly localised terrestrial landscape variables (e.g. slope) and broad scale climate regimes (i.e. precipitation) were found to demonstrate statistically significant influences on canine exposure to environmental Leptospira.

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Page publiée le 25 novembre 2019