Food web connections and the transmission cycles of Trypanosoma cruzi and Trypanosoma evansi (Kinetoplastida, Trypanosomatidae) in the Pantanal Region, Brazil.

We examined by parasitological tests (hemocultures and buffy coat) infection by Trypanosoma cruzi and T. evansi in blood samples from Leopardus pardalis, Cerdocyon thous and domestic dogs. Besides, 25 T. cruzi isolates previously derived from feral pigs and small wild mammals were here characterized by miniexon gene and demonstrated to be in the TcI genotype. Herein, we make an overall analysis of the transmission cycle of both trypanosome species in the light of the assemblage of data collected over the last seven years. The carnivore Nasua nasua was confirmed to play a major role in the transmission cycles of both T. cruzi and T. evansi since it was the species that had the higher prevalence and higher parasitemias by both flagellate species. In addition, our results show that both trypanosomatid species may be found throughout the Pantanal landscape, in all forest strata, as shown by the infection of carnivore, arboreal and terrestrial scansorial marsupial species in complex and seasonal transmission cycles. We propose that transmission of T. cruzi and T. evansi in the southern Pantanal region takes place via an intricate ecological trophic network involving generalist and specialist mammal species that are linked through a robust food-web connection.

Variation in the helminth community structure of Thrichomys pachyurus (Rodentia: Echimyidae) in two sub-regions of the Brazilian Pantanal: the effects of land use and seasonality.

The Pantanal is a large ecosystem located in South America. This preserved area is seasonally flooded due to abundant rainfall during the summer and the subsequent overflow of the Paraguai River. In this paper, we examine the helminth community structure in the wild rodent Thrichomys pachyurus during the wet and dry seasons in two locations of the preserved and cattle ranching areas in the Southern Pantanal. We identified 12 species of helminth, and, although we did not find any differences in species richness between locations within the Pantanal, we found that richness was higher during the wet season. Helminth species were largely aggregated in both farm locations and during seasons. The most common helminth species were more abundant during the dry season than during the wet season, which may have been due to the increased habitat availability and rodent population increase. The intensity of the infection also followed the same pattern for most helminths. The trichostrongylids (Heligmostrongylus crucifer, H. almeidai and Pudica cercomysi) were dominant at both farm locations. The land use of each area was not correlated with helminth diversity. However, species composition of the helminth community of T. pachyurus differed between locations and may be correlated with environmental differences between the habitats. The seasonality of the Pantanal was highly correlated with helminth parasitism in T. pachyurus.

What is the role of small rodents in the transmission cycle of Trypanosoma cruzi and Trypanosoma evansi (Kinetoplastida Trypanosomatidae)? A study case in the Brazilian Pantanal.

Determining the reservoir hosts for parasites is crucial for designing control measures, but it is often difficult to identify the role that each host species plays in maintaining the cycle of infection in the wild. One way to identify potential maintenance hosts is to estimate key parameters associated with transmission and pathogenicity. Here we assess the potential for three native rodent species of the Brazilian Pantanal (Clyomys laticeps, Thrichomys pachyurus and Oecomys mamorae) to act as reservoir or maintenance hosts of Trypanosoma evansi, an important parasite of domestic livestock. By analyzing blood parameters of naturally infected wild-caught rodents of these species, we compared their levels of parasitemia and anemia due to T. evansi infection with literature values for other host species infected by this parasite. We also analyzed levels of these blood parameters relative to infection by Trypanosoma cruzi, the causative agent of Chagas disease in humans, for which wild rodents are already thought to be important reservoir species. All three species showed low impacts of the two trypanosomes on their blood parameters compared to other species, suggesting that they experience a low virulence of trypanosome infection under natural conditions in the Pantanal and might act as maintenance hosts of trypanosome infections. The low parasitemia of trypanosome infections suggests that these rodents play a secondary role in the transmission cycle compared to other species, especially compared to the capybara (Hydrochaeris hydrochaeris) which also experiences low pathogenicity due to infection despite much higher levels of parasitemia.

Variables that modulate the spatial distribution of Trypanosoma cruzi and Trypanosoma evansi in the Brazilian Pantanal.

An evaluation was made on how the landscape and cattle ranching affect the transmission cycles and the patterns of tripanosomatid infection (Trypanosoma cruzi and Trypanosoma evansi) of small wild mammals in the Pantanal. This region comprises a large natural environment with a multiplicity of habitats, wide variety of biodiversity besides the presence of livestock. T. cruzi and T. evansi infections were evaluated by parasitological and serological methods in one preserved and one cattle ranching area. The diversity of the small mammal fauna showed to be the same in the two studied areas, however, their relative abundance was different. Distinct enzootiological scenarios of both trypanosomatids could be observed. Transmission of T. cruzi occurred mainly in forested areas, in the two study areas, while T. evansi occurred dispersed among all habitats studied in the unpreserved area. The arboreal rodent Oecomys mamorae, the most abundant species in both areas, displayed high T. cruzi and T. evansi serum prevalence and parasitemias. Also, the caviomorph rodent Thrichomys pachyurus was shown to be an important host due to its expressive relative abundance, prevalence of infection by both trypanosomatid species and a broad range use of habitats. The role of the small mammal fauna in the transmission cycle of both trypanosomes species seems to be distinct according to land use since we found a broad range of T. evansi infected hosts in the preserved area in contrast to cattle ranching area and a half number of the rodents species infected with T. cruzi in unpreserved in comparison to protect area. The present study showed that cattle ranching in this study area did not enhance overall prevalence of T. cruzi infection among small wild mammals. Together with the observation that small mammals diversity in FA is similar to RN area suggest that ranching activity may also not necessarily conduct to biodiversity loss or risk of Chagas disease.