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Toxoplasmose amazonienne : biodiversité de Toxoplasma gondii chez l’homme et l’animal, conséquences pathologiques et mécanismes de virulence

Abstract : Discovered in 1908 simultaneously in North Africa and Brazil, Toxoplasma gondii is a parasite of warm-blooded vertebrates (mammals and birds). Circulating T.gondii strains in North America and Europe have been grouped into three major clonal lineages: type I (high virulence), type II (intermediate virulence) and type III (low virulence). In French Guiana, the presence of "atypical" strains of T. gondii in wild and domestic animals was prominently reported in the early 2000s. These non-type I, type II or type III strains have a very high pathogenicity, even in immunocompetent persons.10 strains were selected: 5 strains isolated from patients hospitalized at Cayenne Hospital and 5 isolated strains for wild or domestic animals. These strains were compared to 3 reference strains corresponding to the 3 clonal lines. This study included a genetic part (microsatellites, virulence genes, gene expression, DNA microarrays), a virulence part in the mouse model (determination of lethal dose, determination of a predictive virulence score) and an immunological part (cytokines assay).The presence of 'atypical' strains of T. gondii in French Guiana is well established. These strains have unique genetic characteristics outside the usually encountered clonal strains. Although some genes of atypical strains have similarities with strains with low virulence, it is found that this does not decrease their virulence. However, the host's immune response fails to eliminate the infection, which can be serious if left untreated.
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Submitted on : Wednesday, May 27, 2020 - 8:59:09 PM
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Stéphane Simon. Toxoplasmose amazonienne : biodiversité de Toxoplasma gondii chez l’homme et l’animal, conséquences pathologiques et mécanismes de virulence. Médecine humaine et pathologie. Université de Guyane, 2019. Français. ⟨NNT : 2019YANE0001⟩. ⟨tel-02636613⟩

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