RESUMO
In French Guiana, severe cases of toxoplasmosis in immunocompetent patients are associated with atypical strains of Toxoplasma gondii linked to a wild neotropical rainforest cycle and a higher genetic diversity than usually observed for T. gondii isolates from anthropized environment. This raises the question of the impact of anthropization of the natural environment, on genetic diversity and on the population structure of T. gondii. However, few data are available on strains circulating in the anthropized areas from French Guiana. Seropositive animals originating mainly from anthropized sub-urban areas and punctually from wild environment in French Guiana were analyzed for T. gondii isolation and genotyping. Thirty-three strains were obtained by bioassay in mice and compared with 18 previously reported isolates chiefly originating from the Amazon rainforest. The genotyping analysis performed with 15 microsatellite markers located on 12 different chromosomes revealed a lower genetic diversity in the anthropized environment. Results were analyzed in terms of population structure by clustering methods, Neighbor-joining trees reconstruction based on genetic distances, F(ST,) Mantel's tests and linkage disequilibrium. They clearly showed a genetic differentiation between strains associated to the anthropized environment and those associated to the wild, but with some inbreeding between them. The majority of strains from the anthropized environment were clustered into additional lineages of T. gondii that are common in the Caribbean. In conclusion the two environmental populations "wild" and "anthropized" were genetically well differentiated. The anthropization of the environment seems to be accompanied with a decreased diversity of T. gondii associated with a greater structure of the populations. We detected potential interpenetration and genetic exchanges between these two environmental populations. As a higher pathogenicity in human of "wild" genotypes has been described, the interpenetration of both environments leads to hybridization between strains that may be at risk for human health.
Assuntos
Variação Genética , Toxoplasma/genética , Toxoplasmose Animal/parasitologia , Toxoplasmose/parasitologia , Animais , Teorema de Bayes , Análise por Conglomerados , Guiana Francesa , Genótipo , Humanos , Camundongos , Repetições de Microssatélites , Modelos Genéticos , Filogenia , Filogeografia , Polimorfismo Genético , Análise de Componente Principal , Toxoplasma/classificação , Meio SelvagemRESUMO
Six polymorphic microsatellite loci were isolated and characterized using a microsatellite-enriched genomic library from the Chagas' disease vector Triatoma pseudomaculata. This species is found in Brasil in Caatinga areas and predominantly in peridomestic habitats. All the microsatellites tested on a population of T. pseudomaculata sampled in the Bahia State, Brazil, were polymorphic (2-15 alleles). Markers amplification was also tested on six Triatoma species and some loci successfully amplified in the most phylogenetically related species, in particular Triatoma brasiliensis.