A DESCOBERTA DO ESPRITO BRUNO SNELL PDF

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Unravelling T. Trypanosomatids are ancient parasitic eukaryotes that still maintain prokaryotic characteristics. Trypanosoma cruzi , a primarily wild mammal parasite, infected humans already long before European colonization of the Americas.

One of the first biochemical attempts to cluster the T. The description of wild mammal species harboring Z2 two decades later challenged this assemblage attempt.

Currently, the genotypes of T. The biology of T. The study of the transmission cycle among wild animals has broken paradigms and raised new questions: i the interaction of the T. The development of models of environmental variables that determine the spatial distribution of the elements that make up T. There is no way to solve this neglected disease once and for all if not through a multidisciplinary look that takes into account all kinds of human and animal activities in parallel to environmental variations.

In addition to being a successful parasite, T. It was first observed by Carlos Chagas in in the digestive tract of a triatomine Panstrongylus megistus examined after his attention was drawn to insects that sucked people's blood Chagas, Since he was in Lassance, a poor little town in the interior of Minas Gerais State, and did not have laboratory facilities, Chagas asked his mentor and director, Oswaldo Cruz, to put infected triatomines in contact with marmosets Callithrix penicillata.

Three weeks later, Oswaldo Cruz observed trypomastigote forms in the blood of these animals. In contrast to what was thought by Chagas and Cruz that the parasites were transmitted by the insects' bites , the marmosets probably became infected by the ingestion of the infected bugs, resulting in the first demonstration of the oral infection of wild mammals Coura, Oswaldo Cruz urged Carlos Chagas to perform experimental infections in other animals soon done on mice, guinea pigs, rabbits, dogs and monkeys.

In , Carlos Chagas returned to Lassance, where he began to examine animals and humans. First, he identified trypomastigote forms in the blood of a cat; then, also in , he detected the same trypomastigote forms in the blood of a child Chagas, In , Carlos Chagas described the presence of trypomastigotes in the blood of an armadillo and in a specimen of Panstrongylus geniculatus collected in the armadillo's burrow Chagas, Chagas described the acute form of human disease in Coura et al.

Thus, a new species of Trypanosoma , its vector and mammalian hosts, and the human disease due to this trypanosome species were described by the same scientist, an exceptional fact in medicine.

Despite having observed T. In the same manuscript, for the first time, Chagas also suggested, based on the epidemiological data available, that Triatoma infestans was also implicated in T. Later, this triatomine species was recognized as the most important domiciliated vector in several countries of South America. Trypanosoma cruzi belongs to the family Trypanosomatidae, an ancient diverging eukaryotic monophyletic group of parasites that includes monoxenic and heteroxenic species.

Trypanosomes still share many molecular characteristics with both prokaryotes and eukaryotes. Very recently, the meiotic machinery of higher eukaryotes has been described in T. This mechanism was very early described in T. Trypanosomatids are considered important because some of their representatives are etiological agents of important diseases for humans and animals of economic interest.

This broader look also resulted in the awareness that the limits of parasite host specificity may be quite blurred. Thus, since , cases of monoxenic trypanosomatids infecting humans in mixed infections with Leishmania spp. These findings increased in number until the description of a fatal human case of a visceral leishmaniasis-like disease associated with a parasite related to Crithidia spp.

Maruyama et al. Wild free-ranging mammals infected solely by Crithidia mellificae have already been described Rangel et al. These findings, in addition to the consciousness of the multifactorial character of the parasitism phenomenon and its consequences, have broken numerous paradigms. Among them, parasites are necessarily pathogenic agents, the concept of which is a reservoir and the evolution of the parasitism phenomenon, among others.

A broader view of what is parasitism is important in the study of Trypanosoma spp. The importance of the consideration and study of the spatial characteristics in which the encounter between these actors, parasite and host, occurs, is becoming increasingly clear. In this sense, cartographic tools have been contributing to such an extent that they can no longer be dispensed.

Filling in the gaps in the knowledge of these ancient eukaryotic organisms will surely improve our understanding of the complexity of the evolutionary process of living beings in general. In this article, we will focus on Trypanosoma cruzi , not only as the etiological agent of Chagas disease but also as one of the most successful parasite species. We will mention here some key points from the longtime study and debate on the subject that has lasted for over a century Figure 1.

We will also present a current state of the art of the transmission cycle of T. Figure 1. Timeline landmarks of the knowledge of Trypanosoma cruzi biology. In the following decades, some studies conducted especially in Brazil, Colombia, Venezuela and Costa Rica searched for T. However, it was only during the seminal studies conducted by Mauro Pereira Barretto from to in Brazil that this protozoan parasite started to be considered a primarily wild enzootic organism, maintained by wild mammals and triatomines Barretto, a.

Nevertheless, the same author described trypanosomiasis due to T. Influenced by the studies of MP Barretto, the scientific community started to consider that the disruption of the ecological equilibrium in a wild environment could result in outbreaks of human disease. The main aspects observed by Barretto in that time and now observed in the recent Chagas disease outbreaks were i forest fragmentation, reducing areas for mammals and vectors; ii the displacement of host and vectors to new areas; iii proximity to human dwellings and their annexes; iv and the contact between infected vectors and humans or human's prepared food or beverage Barretto, b ; Roque et al.

When Barretto finished his studies, he described more than one hundred mammal species naturally infected by T. At that moment, this trypanosomiasis due to T. A very important landmark in the construction of the knowledge of this parasitosis was the discovery that humans became infected by T.

Cardiac lesions compatible with the clinical outcome of chronic Chagas disease patients were also observed in mummies from the Chilean Atacama Desert Rothhammer et al. In Brazil, the most ancient mummies found infected by this parasite are dated from 7, to 4, years BP and were derived from Central Brazil Lima et al.

Accordingly, the domestication of Cavia sp. The heterogeneity of T. Later, several authors described different patterns of cell growth and differentiation in axenic cultures, demonstrating that the heterogeneity observed was not only morphological but could result in distinct success in replicating and differentiating into infective forms. The first attempt to cluster the observed heterogeneity among T. Three Biodemes were proposed: Biodeme I for strains that resulted in high virulence and mortality in 10—12 dpi; Biodeme II in the cases of mild virulence and mortality after only 20—25 dpi; and Biodeme III, which resulted in a slow increase in parasitemia and no mortality in infected mice Andrade et al.

This proposition, however, was time-consuming, dependent on laboratory animal availability, and isolates certainly underwent selection pressure due to the experimental infection. Brener suggested the classification of two polar types based on morphology and tissue tropism, describing an aggressive pole represented by the Y strain and a benign pole exemplified by the CL strain. The biological, immunological, drug resistance and clinical differences that were being unveiled were so impressive that it was even proposed to consider that T.

The characterization of T. This proposition was certainly one of the most important landmarks in the study of T. This T. The majority of the molecular studies on T. Since their description, the different zymodemes were associated with different transmission cycles: Z1 and Z3 were associated with the transmission cycles in the wild and Z2 in the domestic environment.

The domestic cycle of T. This proposition was supported, in part, by two important features: i T. This subpopulation was therefore associated with the domestic cycle of T.

It was more than two decades later, through the description of a well-established transmission cycle involving free-ranging golden lion tamarins GLTs; Leontopithecus rosalia and T. Moreover, the infection by T. Since these initial findings, T. To date, it has not been possible to unequivocally associate T. The advances of the molecular techniques for T. Soon after the first nomenclature consensus was published, six discrete phylogenetic lineages later named discrete typing units—DTUs were proposed Brisse et al.

This division was based on the second and currently valid nomenclature consensus that divided the T. It is not surprising that TcI was initially associated with the sylvatic cycles because TcI is the most widespread DTU, being detected in all areas of T. This DTU was first associated with opossums; however, while individuals from the Didelphis genus were most commonly infected by TcI Fernandes et al.

The proposed association among TcI, Didelphis sp. Reports on TcII-infected wild mammals are less numerous in comparison to those on TcI, but TcII also presents a noteworthy host range and is widely distributed in nature Jansen et al. TcII is the second most frequently found genotype infecting wild mammals in Brazil, including mammals of the Amazon basin region Lima et al.

Undoubtedly a turning point, an important milestone in the discussion of genetic diversity in T. The description of this phenomenon in some isolates of Ecuador sheds light on a decades-long debate related to the largely clonal character of the taxon.

More intriguing is the description of clonal groups that may occur in sympatry with clonal groups that the authors propose to have experienced in past hybridization events.

These fascinating findings largely explain the extreme diversity of T. Another milestone in the history of the study of T. This finding showed that opossums can act as reservoirs and vectors of T. Opossums, like many other mammals, have a pair of anal glands. These glands have a wrap that is partly made up of a striated muscle layer and a small portion of pearly looking connective tissue.

When threatened or stressed, these animals expel the extremely bad smelling content of these glands as a defense mechanism. Within the scent glands, the flagellates are preferentially disposed around the glandular epithelium, an area rich in hyaluronic acid.

That is, the scent glands do not constitute a reservoir within the reservoir. Interestingly, when injected directly into the scent glands, Leptomonas sp. Taken together, these findings led Deane and coauthors to propose scent glands as the steppingstone for the adaptation of T. Maria Deane and her colleagues conducted a pioneering long-term study on the interaction of T. These studies included experimentally infected animals born in captivity and naturally infected animals.

Didelphid opossums are likely to be ancient T.

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Unravelling T. Trypanosomatids are ancient parasitic eukaryotes that still maintain prokaryotic characteristics. Trypanosoma cruzi , a primarily wild mammal parasite, infected humans already long before European colonization of the Americas. One of the first biochemical attempts to cluster the T. The description of wild mammal species harboring Z2 two decades later challenged this assemblage attempt.

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