Environmental influence on Triatoma vitticeps occurrence and Trypanosoma cruzi infection in the Atlantic Forest of south-eastern Brazil.

Trypanosoma cruzi requires a triatomine insect vector for its life cycle, which can be complex in different enzootic scenarios, one of which is the unique transmission network in the Atlantic Forest of south-eastern Brazil. In Espírito Santo (ES) State, highly infected Triatoma vitticeps are frequently reported invading domiciles. However, triatomines were not found colonizing residences and mammals in the surrounding areas did not present T. cruzi infection. To date, the biotic and abiotic variables that modulate T. vitticeps occurrence and T. cruzi infection in ES State are still unknown. The aim of this study was to identify the environmental variables that modulate their occurrence. Local thematic maps were generated for two response variables: T. vitticeps occurrence and T. cruzi infection. The following explanatory variables were tested: climate (temperature, relative air humidity and rainfall), altitude elevation, mammalian species richness as well as soil and vegetation types. Spatiotemporal distribution patterns and correlation levels between response and explanatory variables were assessed through spatial statistics and map algebra modelling. The central and southern mesoregions presented higher T. vitticeps and T. cruzi distributions and can be considered transmission hotspots. The explanatory variables that can explain these phenomena were relative air humidity, average temperature, soil type, altitude elevation and mammalian species richness. Algebra map modelling demonstrated that central and southern mesoregions presented the environmental conditions needed for T. vitticeps occurrence and T. cruzi infection. The consideration of environmental variables is essential for understanding the T. cruzi transmission cycle. Cartographic and statistical methodologies used in parasitology have been demonstrated to be reliable and enlightening tools that should be incorporated routinely to expand the understanding of vector-borne parasite transmission.

Dissecting the phyloepidemiology of Trypanosoma cruzi I (TcI) in Brazil by the use of high resolution genetic markers.

BACKGROUND: Trypanosoma cruzi, the causal agent of Chagas disease, is monophyletic but genetically heterogeneous. It is currently represented by six genetic lineages (Discrete Typing Units, DTUs) designated TcI-TcVI. TcI is the most geographically widespread and genetically heterogeneous lineage, this as is evidenced by a wide range of genetic markers applied to isolates spanning a vast geographic range in Latin America. METHODOLOGY/PRINCIPAL FINDINGS: In total, 78 TcI isolated from hosts and vectors distributed in 5 different biomes of Brazil, were analyzed using 6 nuclear housekeeping genes, 25 microsatellite loci and one mitochondrial marker. Nuclear markers reveal substantial genetic diversity, significant gene flow between biomes, incongruence in phylogenies, and haplotypic analysis indicative of intra-DTU genetic exchange. Phylogenetic reconstructions based on mitochondrial and nuclear loci were incongruent, and consistent with introgression. Structure analysis of microsatellite data reveals that, amongst biomes, the Amazon is the most genetically diverse and experiences the lowest level of gene flow. Investigation of population structure based on the host species/genus, indicated that Didelphis marsupialis might play a role as the main disperser of TcI. CONCLUSIONS/SIGNIFICANCE: The present work considers a large TcI sample from different hosts and vectors spanning multiple ecologically diverse biomes in Brazil. Importantly, we combine fast and slow evolving markers to contribute to the epizootiological understanding of TcI in five distinct Brazilian biomes. This constitutes the first instance in which MLST analysis was combined with the use of MLMT and maxicircle markers to evaluate the genetic diversity of TcI isolates in Brazil. Our results demonstrate the existence of substantial genetic diversity and the occurrence of introgression events. We provide evidence of genetic exchange in TcI isolates from Brazil and of the relative isolation of TcI in the Amazon biome. We observe the absence of strict associations with TcI genotypes to geographic areas and/or host species.

Trypanosoma cruzi in a caviomorph rodent: parasitological and pathological features of the experimental infection of Trichomys apereoides (Rodentia, Echimyidae).

To understand the interaction of Trypanosoma cruzi with caviomorph rodents, which supposedly have an ancient co-evolutionary history with this parasite, experimental infection of laboratory reared Trichomys apereoides with several isolates of both genotypes of the parasite was studied. Parasitemia, pattern of hematic cells, specific humoral immune response, histopathological features and parasite clearance were appraised. T. apereoides maintained stable infections independent of the T. cruzi genotype as demonstrated by positive PCR results in analyses of several tissues after a 5 months follow-up. The acute phase was characterized by abundant and disseminated presence of amastigotes, vacuolization and/or myocytolysis. Lymphocytosis was a common feature. The chronic phase was characterized mainly by lymphomacroeosinophilic infiltrates independent of the inoculated T. cruzi isolate. T. cruzi of different genotypes did not show any tissular preference in T. apereoides.

Trypanosoma cruzi transmission in a captive primate unit, Rio de Janeiro, Brazil.

A breeding in captivity program of neotropical primates for subsequent reintroduction in nature is in progress at the Primatology Center of Rio de Janeiro (CPRJ). Almost 200 animals of 20 species that include both wild captured animals and specimens born in captivity are maintained in CPRJ. Here, we examined 198 primates of CPRJ for infection with the protozoan parasite Trypanosoma cruzi. The animals included 18 species of eight genera. We also performed an "ad lib" search for triatomines that could be incriminated as putative transmitters of the protozoan in this scenario. Anti-T. cruzi antibodies were observed (by indirect immunofluorescence assay-IFA) in 40 monkeys (26.5%). Four Panstrongylus megistus were collected in the monkey's food storage room near the cages and in human dwellings in the proximity to CPRJ. T. cruzi were isolated from nine primates of two genera (Leontopithecus and Saguinus) and from two individuals of the vector P. megistus. The transmission inside the cages could be attested by the isolation of the T. cruzi from primates born in captivity. Multi-locus enzyme electrophoresis (MLEE) demonstrated that the two isolates from Saguinus bicolor bicolor displayed a zymodeme 1 profile in four out of five tested enzymes, while all isolates derived from Leontopithecus showed zymodeme 2 for four out of the five tested enzymes. Mini-exon gene analysis genotyped all isolates as T. cruzi II, which is associated with human disease in Brazil. A wild primate unit such as CPRJ, located inside the forest and near to human dwellings and with T. cruzi II infected animals, deserves a careful surveillance in order to prevent expansion of the infection.