Home Economics American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research
A marmoset Callithrix penicillata was the first host identified by Carlos Chagas when he discovered a new trypanosome species in Lassance (Minas Gerais state, Brazil), which he named Trypanosoma minasense. Later, investigating the local triatomines, Chagas found flagellates that he inferred to be the intermediate forms of the trypanosomes diagnosed in marmosets. To confirm this hypothesis, Chagas sent some infected bugs to be used to infect groups of Callithrix jacchus that were kept in captivity. Performed by Oswaldo Cruz, this resulted in the visualization of flagellates in the peripheral blood of marmosets displaying morphology quite distinct from T. minansensis: it was the discovery of T. cruzi.59
Since then, different species of Neotropical primates included in Cebidae (monkeys) and Callitrichidae (marmosets) families are commonly found naturally infected by T. cruzi.19 Widespread in the Americas, these primates occupy different forest strata and have varied feeding habits, including species that feed on invertebrates and small mammals, which facilitate T. cruzi transmission by the oral route. Their nightly refuges in hollow trees are often shared with triatomine bugs, which allows (or propitiates) vectorial contaminative transmission of the parasite to these mammalian species.42
The infection prevalence in primates varies between 4% and 88% and can be quite elevated in tamarins.60,61 Both the prevalence of infection and the transmissibility potential of the parasite by the host (attested by positive hemocultures) may vary according to gender, age, species, coinfection with other parasites and general health, ecological characteristics, and origin of the studied population. Even as an important point in parasitism phenomenon, the effects of concomitant parasitic infections on the host are attracting the attention. A positive association between the presence of trichostrongilid nematode infection and positive hemocultures, has already been described in lion tamarins Leontophitecus rosalia and Leontophitecus chrysomelas that are endangered callitrichidae species endemic to the Atlantic forest.62
In the Poco das Antas National Reserve (Rio de Janeiro, Brazil), the Golden lion tamarin (Leontophitecus rosalia) (Fig. 11.4) acts as an important Trypanosoma cruzi reservoir since it displays a high prevalence of seropositive animals and high rates of positive hemoculture (46%). Tamarins live in quite stable social groups and are extremely territorial. The members of the groups share tasks like carrying the newborns. The T. cruzi infection prevalence is not homogeneously distributed among the Tamarin social groups and, in fact, the prevalence of infection varies among the different social groups from the Poco das Antas National Reserve. The aggregated character of the T. cruzi infection among the tamarin groups is probably due to microenvironmental peculiarities, since these tamarins display no expressive
Figure 11.4 Golden lion tamarin Leonthopitecus rosalia from Silva Jardim, Brazil. Photo: Rodrigo Mexas.
genetic heterogeneity.63 This prevalence of infection was found to be quite distinct from other areas, adjacent to the reserve, where the same species L. rosalia presents low prevalence of T. cruzi infection, reinforcing the nidal characteristic of the parasite maintenance in nature. This tamarin population could be monitored annually for 10 years and has proved to be the more conspicuous focus of T. cruzi DTU TcII transmission and maintenance in this wild environment. Indeed L. rosalia demonstrated to be able to maintain long-lasting infections with significant rates of positive hemocultures by this DTU formerly associated to the domestic transmission cycle. An interesting aspect is that the authors observed 3-year variations in rates of blood cultures of the tamarin of the Biological reserve of Poco das Antas.61
High positive hemoculture prevalence was also observed in the sibling tamarin species Leontopithecus chrisomellas in a biological reserve located in Una, Bahia state in a Brazilian northeastern fragment of the Atlantic coastal rain forest. The absolute majority of the T. cruzi isolates derived from both tamarin species were characterized as DTU TcII. The DTU Tcl was observed in other species of nonprimate mammals from the Poco das Antas and in a dozen tamarins of both biological reserves.61
The infection of primates is not primordially by the DTU TcII of the parasite, but many other primate species, besides Leontophitecus spp. have been found naturally infected with T. cruzi DTU TcII in different regions of Brazil, from the Atlantic to the Amazon region.19 The DTUs TcIII/IV described as genotype Z3 of the parasite has also been found in primates, but this finding is still restricted to the Amazon region.64
An important feature that has to be taken in consideration is that several Neotropical primates are threatened species submitted to conservation programs, as is the case of the Golden lion tamarin. These programs often include exchange, translocation, and reintroduction of animals, without considering the prevalence and pattern of infection by parasites such as T. cruzi. Such programs can lead to an introduction of infected mammals in untouched areas and trigger the establishment of new transmission cycles in other areas. Also, the concentration of primate groups of different origin in the same preservation reserve will increase the probability of infection of the threatened species.
Experimental studies in Neotropical (Cebus sp., Callithrix sp., and Saimiri sp.) and African (Macaca mulatta) primates show that infection by Trypanosoma cruzi in these mammalian species presents some similarities with Chagas disease, such as a low frequency of cardiac abnormalities and the rare occurrence of megasyndromes and systemic changes. Electrocardiographic alterations observed were the low voltage of T- and R-waves and high voltage of V3 wave, all of them in DII65
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