Trypanosoma cruzi in the sylvatic environment: distinct transmission cycles involving two sympatric marsupials.

Thirty-five specimens of Philander frenata and 36 Didelphis marsupialis were captured in the same Atlantic forest area of Brazil between 1992 and 1994. Haemocultures showed that 50% of P. frenata and 60% of D. marsupialis were infected with Trypansoma cruzi. Biological, biochemical and molecular characterization of the isolates suggested 2 distinct transmission cycles of T. cruzi occurred between these 2 sympatric didelphids. The T. cruzi isolates could be distinguished according to their association with each marsupial species. Biochemical characterization (multilocus enzyme electrophoresis) revealed 15 zymodemes; more variability was observed among the P. frenata isolates than among the isolates from D. marsupialis. The course of natural and experimental infection in D. marsupialis and P. frenata was different and suggested that D. marsupialis was more resistant to infection than P. frenata. In the studied area, P. frenata seems to be a more important reservoir of T. cruzi than D. marsupialis, since 40% of the characterized isolates from P. frenata belonged to the T. cruzi II group, which is associated with human infections.

Cerebral aneurysmal dilatation in an infant with perinatally acquired HIV infection and HSV encephalitis.

Although most children with human immunodeficiency virus (HIV) infection have neurological dysfunction, in childhood the incidence of symptomatic cerebrovascular disease is low. Cerebral aneurysmal arteriopathy in childhood AIDS has been reported in the past and considered to have a relatively long latency following the primary infection. We report a 1 month-old infant with congenitally acquired HIV infection, and herpes encephalitis; she presented a sudden cardiorespiratory arrest followed by coma and was found to have a giant saccular aneurysm of the left basilar artery. Literature review showed that cerebral aneurysmal artheriopathy is an unusual manifestation in newborns and infants and this case is possibly the youngest patient reported with aneurysma, herpes encephalitis and AIDS. The role of HIV and herpes simplex infections in the pathogenesis of this lesion is discussed.

The coati (Nasua nasua, Carnivora, Procyonidae) as a reservoir host for the main lineages of Trypanosoma cruzi in the Pantanal region, Brazil.

We have focused on the role played by a carnivore, the coati (Nasua nasua), in the transmission cycle of Trypanosoma cruzi in the Brazilian Pantanal biome. We collected data during 2000/01 and 2005-07. Prevalence and pattern of T. cruzi infection were determined by serological tests and hemoculture. Isolates were characterized by miniexon molecular assay. Our results demonstrate that T. cruzi transmission cycle among coatis in the southern Pantanal seems to be well established, as we found high serum prevalences and high parasitemias throughout the two studied periods. Single infections by TCII (32.1%), TCI (28.0%) and Z3 (7.1%) were observed. Mixed infections by TCI/TCII (10.7%) and TCI/Z3 (3.6%) were also detected. Distinct genotypes of T. cruzi could be recovered during the 8 months follow-up of the same animals. As free-living coatis have high densities and inhabit all habitats, they may play an important role in the maintenance and dispersion of the main T. cruzi subpopulations. Considering that the Pantanal connects some of the major biomes of South America, it may be acting as a corridor for the spread of the main T. cruzi subpopulations. Our data give support that predator-prey links are important mechanisms for T. cruzi transmission and perpetuation in the wild.

Humoral immune response kinetics in Philander opossum and Didelphis marsupialis infected and immunized by Trypanosoma cruzi employing an immunofluorescence antibody test.

Philander opossum and Didelphis marsupialis considered the most ancient mammals and an evolutionary success, maintain parasitism by Trypanosoma cruzi without developing any apparent disease or important tissue lesion. In order to elucidate this well-balanced interaction, we decided to compare the humoral immune response kinetics of the two didelphids naturally and experimentally infected with T. cruzi and immunized by different schedules of parasite antigens, employing an indirect fluorescence antibody test (IFAT). Both didelphids responded with high serological titers to different immunization routes, while the earliest response occurred with the intradermic route. Serological titers of naturally infected P. opossum showed a significant individual variation, while those of D. marsupialis remained stable during the entire follow-up period. The serological titers of the experimentally infected animals varied according to the inoculated strain. Our data suggest that (1) IFAT was sensitive for follow-up of P. opossum in natural and experimental T. cruzi infections; (2) both P. opossum and D. marsupialis are able to mount an efficient humoral immune response as compared to placental mammals; (3) experimentally infected P. opossum and D. marsupialis present distinct patterns of infection, depending on the subpopulation of T. cruzi, (4) the differences observed in the humoral immune responses between P. opossum and D. marsupialis, probably, reflect distinct strategies selected by these animals during their coevolution with T. cruzi.

The complexity of the sylvatic cycle of Trypanosoma cruzi in Rio de Janeiro state (Brazil) revealed by the non-transcribed spacer of the mini-exon gene.

American trypanosamiasis occurs in nature as a sylvatic cycle, where Trypanosoma cruzi interacts with wild triatomines and mammalian reservoirs, such as marsupials, rodents, armadillos and other animals. Due to difficulties in trying to isolate T. cruzi stocks from the sylvatic cycle, very few studies have been performed in order to understand the parasite infection in natural environments. Traditionally T. cruzi has been considered to be composed of a highly heterogeneous population of parasites. In contrast, the mini-exon and the 24S alpha rRNA gene loci have shown that T. cruzi stocks can be clustered in 2 major phylogenetic groups: lineage 1 and lineage 2. In this report, 68 recently isolated T. cruzi samples from the sylvatic cycle belonging to different geographical areas in Rio de Janeiro, Brazil, have been typed based on a variable spot in the non-transcribed spacer of the mini-exon gene. Eight isolates were from triatomines, 26 stocks were from golden-lion tamarins, 31 from opossums, 2 from rodents and 1 from a three-toed sloth. Thirty (44%-30/68) isolates were typed as lineage 1, while 36 (53%-36/68) isolates were typed as lineage 2. Two opossums presented mixed infection. Therefore, 3% (2/68) of the isolates were typed as lineage 1 + lineage 2. Using these geographical regions as models of sylvatic environments, it was observed that 96% of the Didelphis marsupialis were infected by lineage 2 isolates, while all 26 golden-lion tamarins were infected by lineage 1. The results show preferential association of the 2 lineages of T. cruzi with different hosts, composing the complexity of the sylvatic cycle.