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Écologie et évolution de coronavirus dans des populations de chauves-souris des îles de l’ouest de l’océan indien

Abstract : Zoonoses account for 60% of emerging infectious diseases, among which 70% originate from wildlife. Bats host many infectious agents, including viruses responsible for zoonoses in humans such as Ebola, Nipah or Hendraus. For the last two decades, new bat viruses have emerged in human and animal populations, causing major threats for public and animal health. Coronaviruses (CoV) such as Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS) and Acute Acute Diarrhea Syndrome (SADS) are responsible for thousands of deaths in humans and pigs. Although many studies have described bat CoVs around the world, current knowledge about the diversity and risks associated with emerging CoVs in island ecosystems remain to be precisely assessed.In this work, we investigated the ecology and evolution of coronaviruses in bats by assessing the level of bat exposure to CoVs, and the evolutionary history in the phylogeographic context of the islands of the Western Indian Ocean. Based on the molecular screening of 1088 samples, we report, for the first time the presence of CoVs in insectivorous bats on Mayotte, on Madagascar, in Mozambique and on Reunion Island. The overall prevalence of bats positive for CoV was 8.0% ± 1.2%, with significant variation between continental Africa and islands, as well as between bat families. We found a large diversity of α-CoVs and β-CoVs, some being genetically related to those detected in human (e.g. HCoV-NL63, HCoV-229E, MERS-CoV). These CoVs were phylogenetically structured by bat family, supporting a long history of co-evolution between bats and their associated CoVs in the region. We then focused on the Reunion free tailed bat (Mormopterus francoismoutoui), an endemic species on this island, and investigated temporal infection dynamics in a maternal colony, during two consecutive years. Results highlighted a major variation in the prevalence of infected bats during the maternity season, with patterns similar for both years and the presence of two peaks of infection. Indeed, one pic occurs during the colonization of the maternity colony (associated to an increase in host density), and another about a month after the beginning of parturition (potentially associated to a loss of maternal antibodies in newborns). This work provides strong support for a long history of coevolution between bats and their CoVs in the Western Indian ocean, although within-island speciation for each bat families also occurs. Ecological and biological factors influencing the infection dynamics highlights a different level of CoV transmission risks to other hosts, including humans, associated to bat communities inhabiting each island, as well as to temporal variations in host population structure.
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Submitted on : Tuesday, September 29, 2020 - 1:02:36 AM
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Léa Joffrin. Écologie et évolution de coronavirus dans des populations de chauves-souris des îles de l’ouest de l’océan indien. Ecologie, Environnement. Université de la Réunion, 2019. Français. ⟨NNT : 2019LARE0039⟩. ⟨tel-02951814⟩



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