Browsing by Autor "Vera Valente"

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Chagas Disease in the Amazon Basin: Association of Panstrongylus geniculatus (Hemiptera: Reduviidae) with Domestic Pigs
(Oxford University Press, 1998) Vera Valente; Sebastião Aldo S. Valente; François Noireau; H. Carrasco; Michael A. Miles
Just over 100 autochthonous cases of Chagas disease are reported from the Brazilian Amazon Basin. Panstrongylus geniculatus (Latreille) occurs throughout the region and is the known vector of Trypanosoma cruzi, principal zymodeme 3 (Z3) to the armadillo Dasypus novemcinctus. In the small riverine community of Furo do Rio Pau Grande, pigsties adjoining houses were heavily infested with P. geniculatus, which repeatedly attacked local inhabitants. Palm trees in the immediate vicinity were also infested. T. cruzi principal zymodeme 1 (Z1) was isolated from P. geniculatus, domestic pigs, and opossums, but no human infections were detected. The threat of endemic Chagas disease to the Amazon Basin from either domiciliation of local silvatic triatomine species, or from migration of domestic vectors, demands a program of vigilance and plans of action to eliminate household triatomine colonies.
Genome-Scale Multilocus Microsatellite Typing of Trypanosoma cruzi Discrete Typing Unit I Reveals Phylogeographic Structure and Specific Genotypes Linked to Human Infection
(Public Library of Science, 2009) Martin Llewellyn; Michael A. Miles; H. Carrasco; Michael D. Lewis; Matthew Yeo; Jorge Vargas; Faustino Torrico; Patricio Diosque; Vera Valente; Sebastião Aldo da Silva Valente
Trypanosoma cruzi is the most important parasitic infection in Latin America and is also genetically highly diverse, with at least six discrete typing units (DTUs) reported: Tc I, IIa, IIb, IIc, IId, and IIe. However, the current six-genotype classification is likely to be a poor reflection of the total genetic diversity present in this undeniably ancient parasite. To determine whether epidemiologically important information is "hidden" at the sub-DTU level, we developed a 48-marker panel of polymorphic microsatellite loci to investigate population structure among 135 samples from across the geographic distribution of TcI. This DTU is the major cause of resurgent human disease in northern South America but also occurs in silvatic triatomine vectors and mammalian reservoir hosts throughout the continent. Based on a total dataset of 12,329 alleles, we demonstrate that silvatic TcI populations are extraordinarily genetically diverse, show spatial structuring on a continental scale, and have undergone recent biogeographic expansion into the southern United States of America. Conversely, the majority of human strains sampled are restricted to two distinct groups characterised by a considerable reduction in genetic diversity with respect to isolates from silvatic sources. In Venezuela, most human isolates showed little identity with known local silvatic strains, despite frequent invasion of the domestic setting by infected adult vectors. Multilocus linkage indices indicate predominantly clonal parasite propagation among all populations. However, excess homozygosity among silvatic strains and raised heterozygosity among domestic populations suggest that some level of genetic recombination cannot be ruled out. The epidemiological significance of these findings is discussed.