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Bonamia ostreae

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Isabelle Arzul – 1st expert on this subject based on the ideXlab platform

  • An eDNA/eRNA-based approach to investigate the life cycle of non-cultivable shellfish micro-parasites: the case of Bonamia ostreae, a parasite of the European flat oyster Ostrea edulis.
    Microbial biotechnology, 2020
    Co-Authors: Nicolas Merou, Cyrielle Lecadet, Stephane Pouvreau, Isabelle Arzul

    Abstract:

    Environmental DNA approaches are increasingly used to detect microorganisms in environmental compartments, including water. They show considerable advantages to study non-cultivable microorganisms like Bonamia ostreae, a protozoan parasite inducing significant mortality in populations of flat oyster Ostrea edulis. Although B. ostreae development within the host has been well described, questions remain about its behaviour in the environment. As B. ostreae transmission is direct, seawater appears as an interesting target to develop early detection tools and improve our understanding of disease transmission mechanisms. In this context, we have developed an eDNA/eRNA approach allowing detecting and quantifying B. ostreae 18S rDNA/rRNA as well as monitoring its presence in seawater by real-time PCR. B. ostreae DNA could be detected up to 4 days while RNA could be detected up to 30 days, suggesting a higher sensitivity of the eRNA-based tool. Additionally, more than 90% of shed parasites were no longer detected after 2 days outside the oysters. By allowing B. ostreae detection in seawater, this approach would not only be useful to monitor the presence of the parasite in oyster production areas but also to evaluate the effect of changing environmental factors on parasite survival and transmission.

  • an edna erna based approach to investigate the life cycle of non cultivable shellfish micro parasites the case of Bonamia ostreae a parasite of the european flat oyster ostrea edulis
    Microbial Biotechnology, 2020
    Co-Authors: Nicolas Merou, Cyrielle Lecadet, Stephane Pouvreau, Isabelle Arzul

    Abstract:

    Environmental DNA approaches are increasingly used to detect microorganisms in environmental compartments, including water. They show considerable advantages to study non-cultivable microorganisms like Bonamia ostreae, a protozoan parasite inducing significant mortality in populations of flat oyster Ostrea edulis. Although B. ostreae development within the host has been well described, questions remain about its behaviour in the environment. As B. ostreae transmission is direct, seawater appears as an interesting target to develop early detection tools and improve our understanding of disease transmission mechanisms. In this context, we have developed an eDNA/eRNA approach allowing detecting and quantifying B. ostreae 18S rDNA/rRNA as well as monitoring its presence in seawater by real-time PCR. B. ostreae DNA could be detected up to 4 days while RNA could be detected up to 30 days, suggesting a higher sensitivity of the eRNA-based tool. Additionally, more than 90% of shed parasites were no longer detected after 2 days outside the oysters. By allowing B. ostreae detection in seawater, this approach would not only be useful to monitor the presence of the parasite in oyster production areas but also to evaluate the effect of changing environmental factors on parasite survival and transmission.

  • is pallial mucus involved in ostrea edulis defenses against the parasite Bonamia ostreae
    Journal of Invertebrate Pathology, 2020
    Co-Authors: Bruno Chollet, Maria Pradoalvarez, Ophelie Gervais, Sergio Fernandezboo, Stephane Claverol, Cyrielle Lecadet, Christine Dubreuil, Isabelle Arzul

    Abstract:

    Abstract Bonamia ostreae is an intrahemocytic parasite that has been responsible for severe mortalities in the flat oyster Ostrea edulis since the 1970s. The Pacific oyster Crassostrea gigas is considered to be resistant to the disease and appears to have mechanisms to avoid infection. Most studies carried out on the invertebrate immune system focus on the role of hemolymph, although mucus, which covers the body surface of molluscs, could also act as a barrier against pathogens. In this study, the in vitro effect of mucus from the oyster species Ostrea edulis and C. gigas on B. ostreae was investigated using flow cytometry. Results showed an increase in esterase activities and mortality rate of parasites exposed to mucus from both oyster species. In order to better understand the potential role of mucus in the defense of the oyster against parasites such as B. ostreae, liquid chromatography and tandem mass spectrometry were used to describe and compare mucus protein composition from both species. In all oyster species, pallial mucus contains a high level of proteins; however, O. edulis mucus produced a variety of proteins that could be involved in the immune response against the parasite, including Cu/Zn extracellular superoxide dismutase, thioxiredoxin, peroxiredon VI, heat shock protein 90 as well as several hydrolases. Conversely, a different set of antioxidant proteins, hydrolases and stress related proteins were identified in mucus from C. gigas. Our results suggest an innate immunity adaptation of oysters to develop a specific response against their respective pathogens. The mucosal protein composition also provides new insights for further investigations into the immune response in oysters.

Benjamin Morga – 2nd expert on this subject based on the ideXlab platform

  • Etude des interactions hôte/parasite chez l’huître plate Ostrea edulis et son parasite Bonamia ostreae, Study of host/parasite interactions in the flat oyster Ostrea edulis and the parasite Bonamia ostreae
    , 2020
    Co-Authors: Benjamin Morga

    Abstract:

    The history of the French oyster production highlights the fragility of this production against overexploitation and disease outbreaks. In particular, the production of flot oyster, Ostrea edulis, has decreased following the emergence of two parasitic diseases including bonamiosis. The means to fight against bonamiosis are relatively limited. They are mainly based on oyster health surveillance to limit the spread of the disease. However, the use of predictive models of disease progression in infected area would help to improve stock management and minimize the impact pathogens. Moreover the development of resistant animais could help to revive this production. These different approaches require appropriate diagnostic tools, a good knowledge of the life cycle of the pathogen, and the interactions between the parasite and its host. In this context, the main objective of the phD work is to understand the interactions between the fiat oyster Ostrea edulis and the parasite Bonamia ostreae, and particularly the molecular basis of the resistance to the parasite. In a first step, a subtractive cDNA bank allowed the identification of ESTs differentially expressed in haemocytes in response to the parasite. Expression of some genes, among which a galectin, was measured by Real lime PCR in the context of in vitro infections. In addition, the cellular response was investigated by flow cytometry and the infection was checked by microscopy. These experiments showed a multiplication of the parasite inside haemocytes assoclated with a decreased of esterases and of the production of ROS. In a second step, a comparative approach was carried out between a population of oysters resistant to bonamiosis and a natural population. Results suggest that modulation of apopotosis and decrease of phagocytosis could be involved in mechanisms related to resistance to bonamiosis…

  • contribution of in vivo experimental challenges to understanding flat oyster ostrea edulis resistance to Bonamia ostreae
    Frontiers in Cellular and Infection Microbiology, 2017
    Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Sylvie Lapegue, Estelle Harrang, Bruno Chollet, Isabelle Arzul

    Abstract:

    Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analysed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analysed by flow cytometry. Four genes homologous to genes shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls, phagocytosis allow parasite degradation, but it also contribute to spreading of B. ostreae infection. Infected selected oyster show a lower phagocytosis activity might be a solution against the parasite infection. The expression of the OeIAP gene and OeFas-ligand gene was significantly increased in selected oysters at 5 days post injection. OeIAP gene expression appeared significantly increased in wild-type oysters at 8 days post injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.

  • Contribution of in Vivo Experimental Challenges to Understanding Flat Oyster Ostrea edulis Resistance to Bonamia ostreae
    Frontiers in Cellular and Infection Microbiology, 2017
    Co-Authors: Benjamin Morga, Tristan Renault, Barthelemy Chollet, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Sylvie Lapegue, Estelle Harrang, Isabelle Arzul

    Abstract:

    Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in European flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand the mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analyzed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analyzed by flow cytometry. Four genes homologous to those shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD, and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls. Infected selected oyster show a lower phagocytosis activity which might be a protection against the parasite infection. The expression of OeIAP and OeFas-ligand gene was significantly increased in selected oysters at 5 days post-injection. OeIAP gene expression appeared to be significantly increased in wild-type oysters at 8 days post-injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.

Tristan Renault – 3rd expert on this subject based on the ideXlab platform

  • contribution of in vivo experimental challenges to understanding flat oyster ostrea edulis resistance to Bonamia ostreae
    Frontiers in Cellular and Infection Microbiology, 2017
    Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Sylvie Lapegue, Estelle Harrang, Bruno Chollet, Isabelle Arzul

    Abstract:

    Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analysed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analysed by flow cytometry. Four genes homologous to genes shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls, phagocytosis allow parasite degradation, but it also contribute to spreading of B. ostreae infection. Infected selected oyster show a lower phagocytosis activity might be a solution against the parasite infection. The expression of the OeIAP gene and OeFas-ligand gene was significantly increased in selected oysters at 5 days post injection. OeIAP gene expression appeared significantly increased in wild-type oysters at 8 days post injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.

  • Contribution of in Vivo Experimental Challenges to Understanding Flat Oyster Ostrea edulis Resistance to Bonamia ostreae
    Frontiers in Cellular and Infection Microbiology, 2017
    Co-Authors: Benjamin Morga, Tristan Renault, Barthelemy Chollet, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Sylvie Lapegue, Estelle Harrang, Isabelle Arzul

    Abstract:

    Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in European flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand the mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analyzed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analyzed by flow cytometry. Four genes homologous to those shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD, and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls. Infected selected oyster show a lower phagocytosis activity which might be a protection against the parasite infection. The expression of OeIAP and OeFas-ligand gene was significantly increased in selected oysters at 5 days post-injection. OeIAP gene expression appeared to be significantly increased in wild-type oysters at 8 days post-injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.

  • flat oyster follows the apoptosis pathway to defend against the protozoan parasite Bonamia ostreae
    Fish & Shellfish Immunology, 2016
    Co-Authors: Ophelie Gervais, Bruno Chollet, Tristan Renault, Isabelle Arzul

    Abstract:

    The in vitro model Ostrea edulis hemocyte – Bonamia ostreae is interesting to investigate host-parasite interactions at the cellular level. Indeed, this unicellular parasite infects the flat oyster Ostrea edulis and multiplies within hemocytes, the central effectors of oyster defenses. Apoptosis is a mechanism used by many organisms to eliminate infected cells. In order to study the potential involvement of this mechanism in the oyster response to B. ostreae, in vitro experiments were carried out by exposing hemocytes from the naturally susceptible oyster O. edulis and a resistant oyster species Crassostrea gigas to live and heat-inactivated parasites. Hemocyte apoptotic response was measured using a combination of flow cytometry and microscopy analyses. Whatever the host species was, the parasite was engulfed in hemocytes and induced an increase of apoptotic parameters including intracytoplasmic calcium concentration, mitochondrial membrane potential or phosphatidyl-serine externalization as well as ultrastructural modifications. However, the parasite appears more able to infect flat oyster than cupped oyster hemocytes and the apoptotic response was more important against live than dead parasites in the natural host than in C. gigas. Our results suggest that O. edulis specifically responds to B. ostreae by inducing apoptosis of hemocytes.