Characterization and diversity of mechanisms of mortality syndrome affecting juvenile Crassostrea gigas

Infectious diseases are very often explored using reductionist approaches, despite repeated evidence showing them to be strongly influenced by numerous interacting host and environmental factors. Many diseases with complex etiology therefore remain misunderstood. In this thesis, by developing a holi...

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Bibliographic Details
Main Author: Lucasson, Aude
Other Authors: Interactions Hôtes-Pathogènes-Environnements (IHPE), Université de Perpignan Via Domitia (UPVD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Université Montpellier, Guillaume Mitta
Format: Doctoral or Postdoctoral Thesis
Language:French
Published: HAL CCSD 2018
Subjects:
Multifactorial diseases
Pathosystem
Oysters
Transcriptome
Microbiota structure
Ngs
Maladie multifactorielle
Pathosystème
Huîtres
Structure du microbiote
Séquençage haut débit
[SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology
Pacific
Crassostrea gigas
Pacific oyster
Online Access:https://theses.hal.science/tel-02063435
https://theses.hal.science/tel-02063435/document
https://theses.hal.science/tel-02063435/file/2018_LUCASSON_archivage.pdf
Description
Summary:Infectious diseases are very often explored using reductionist approaches, despite repeated evidence showing them to be strongly influenced by numerous interacting host and environmental factors. Many diseases with complex etiology therefore remain misunderstood. In this thesis, by developing a holistic approach to tackle the complexity of the interaction, (i) we deciphered the complex intra-host interactions underlying the Pacific oyster mortality syndrome affecting juveniles of Crassostrea gigas, the main oyster species exploited worldwide and (ii) we validated this mechanism in different infectious environments and oyster genotypes. Using ecologically realistic experimental infections combined with thorough molecular (metabarcoding, transcriptomics, pathogen monitoring) and histological analyses on oyster families with contrasting susceptibilities, we demonstrated that the disease is caused by a multiple infection whose initial and necessary step is the infection of oyster haemocytes by a herpesvirus. Viral replication leads to an immune-compromised state of the host, evolving toward subsequent bacteremia by opportunistic bacteria. By identifying critical intra-host interactions between microorganisms and host immunity, this study cracks the code of the Pacific oyster mortality syndrome and provides important molecular data for the design of prophylactic measures and breeding programs dedicated to the production of oysters resistant to the mortality syndrome. We believe that such a systems biology approach could be applied to decipher other multi-factorial diseases that affect non-model invertebrate species worldwide. Les maladies infectieuses sont souvent étudiées à l'aide d'approches réductionnistes alors qu'elles sont fortement influencées par de nombreux facteurs hôtes et environnementaux en interaction. Ainsi, de nombreuses maladies d’étiologie complexe restent difficiles à caractériser. En développant une approche holistique pour aborder la complexité de l'interaction, (i) nous avons déchiffré les ...

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