Eco-epidemiology of endemic leptospires in the Indian Ocean: bacteria posing risks to human populations
The ECOSPIR project aims to study the biological cycles of leptospires in our environment and to identify biotic conditions (related to the biology of reservoir animals) and abiotic conditions (inter-island exchanges, environmental conditions increasing contamination) that may favor the transmission of these pathogenic leptospires to humans.
Leptospirosis is a major public health problem in the Indian Ocean islands, which have some of the highest annual incidences in the world. Therefore, this project falls within Priority 3 of the S3, and more specifically within the framework of action sheet No. 2, which concerns the prevention of risks and diseases. Studies conducted on this major regional medical interest pathology have revealed distinct transmission cycles on different islands in the Indian Ocean: Madagascar hosts an incredible diversity of pathogenic leptospires, including an endemic species responsible for 15% of human leptospirosis on the neighboring island of Mayotte; in contrast, in Reunion Island and the Seychelles, the disease is mainly caused by a single species of leptospire introduced recently. Operationally, data generated on these islands show that rats are not the only animals involved in transmission to humans, suggesting instead the involvement of other reservoir animals. These studies, conducted within a "One Health" conceptual framework, demonstrate that investigating the environmental compartment of a zoonosis helps elucidate transmission cycles at work in each ecosystem and, beyond that, contribute to guiding control strategies by adapting them to each environment.
The ECOSPIR project unfolds in natural environments (Action 1) by complementing environmental data in insufficiently explored territories (notably the Comoros), and by describing the spatio-temporal dynamics of leptospire infection in natural populations of Reunionese bats. This project also valorizes the bank of leptospires established through the POCT LeptOI project and seeks, through the implementation of new experimental and genomic approaches, to identify the genes responsible for the virulence and host specificity of leptospires in our region (Action 2). Beyond these operationally important outcomes, this ambitious program has allowed the UMR PIMIT and its partners to establish and even increase recognized expertise in investigating zoonotic diseases within the "One Health" conceptual framework.
