Leptospirosis in the Seychelles : geographic, molecular and epidemiological investigations of a zoonotic disease in a tropical insular environment

• Main Author: Biscornet, Leon
• Other Authors: Processus Infectieux en Milieu Insulaire Tropical (PIMIT), Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM)-IRD-Centre National de la Recherche Scientifique (CNRS), Université de la Réunion, Pablo Tortosa
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2020
• Subjects: Leptospirosis; Molecular epidemiology; Seychelles; Rattus; Zoonoses; One health; Animal reservoirs; Leptospira; Réservoirs animaux; Leptospirose; Épidemiologie moléculaire; [SDV.MHEP]Life Sciences [q-bio]/Human health and pathology; Rattus rattus
• Online Access: https://theses.hal.science/tel-02952395; https://theses.hal.science/tel-02952395/document; https://theses.hal.science/tel-02952395/file/2020LARE0013LBiscornet.pdf

Leptospirosis is an emerging neglected disease representing a heavy burden in the tropics, especially in tropical islands such as Seychelles, which record among the highest human incidence worldwide. This thesis aims at exploring the eco-epidemiology of leptospirosis in Seychelles by (i) using rats as markers of environmental exposure to Leptospira infection, (ii) describing the molecular epidemiology of the disease in humans and animals in a One Health framework, and (iii) identifying occupational and behavioural risk factors while comparing the current situation to that described 25 years ago. The combination of fine spatial distribution, molecular and clinical epidemiology complement each other in providing a comprehensive picture of the continuum involving reservoirs and human hosts within a shared environment.Habitat fragmentation and proximity to nutritional sources are found good predictors of Leptospira-laden Rattus spp. Geospatial analyses determined a selection of other important variable factors that are strongly correlated with Leptospira infection in Rattus spp., including altitude or distance to surface water (negative correlation), urbanization and heavy rainfall (positive correlation). Results of these analyses can guide policy makers and especially urban planners to best implement landscape structures for conservation or pest control goals leading to reduced exposure of humans to rat-borne diseases.Rattus norvegicus is found significantly more infected than Rattus rattus. Therefore, increased infection in urbanized/fragmented habitats may result at least in part from Rattus spp distribution, as R. norvegicus is mostly found in urban areas. Most importantly, genotyping of Leptospira in human acute cases and rats suggests that these rodents are involved in only a third of human acute infections, while most human cases originate from yet to be identified reservoir(s).An annual incidence of 54.6 (95% CI 40.7-71.8) per 100,000 confirms the major medical and public health importance of the disease in ...