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Order Carnivora

Carnivores are also a very heterogeneous group that includes meat eaters, as diverse as the grizzly bear, the skunks, weasels, coatis, and wild and domestic dogs and cats. Besides predating other vertebrates, carnivores complete their diet feeding also on plant, fruits, and insects, among others food items. In fact, many representatives of the carnivores are opportunistic feeders. Their common trait is the presence of five finger feet presenting claws and a typical denture comprising teeth adapted to tear. Highly persecuted due to their livestock predation potential and human atavistic fear, among other reasons, this has resulted in many of the big carnivore species being near to extinction. Wild carnivores such as the ocelot (Leopardus pardalis), the coati (Nasua nasua), the raccoon (Procyon lotor), the weasel (Eira barbara), and crab-eating fox (Cerdocyon thous) have been found naturally infected with

18,31,66

Trypanosoma cruzi.

Some of them, like the coati and the weasel, are found both on the ground and in the canopy of trees, acting as bridge hosts, favoring parasite spread among the different forest strata. Coatis, in particular, build their nests in treetops that can be 20 m from ground. Carnivores have important body mass and large life areas that are important traits that enhance acquisition and spreading of parasites, resulting in their potential competence as amplifier reservoirs. Large and medium sized carnivores are known to be top predators of their food chain that usually include smaller mammals that may be infected by T. cruzi.66 Thus, although the contaminative vectorial transmission also occurs, the most common way of infection for these mammalian species, as for any other predator in nature, seems to be the oral route through ingestion of infected mammals or triatomine since several carnivore species are avid insect consumers.66,67

In the Brazilian Pantanal/Chaco region (marshland), the coati species Nasua nasua (Fig. 11.5) was demonstrated to be the main Trypanosoma cruzi reservoir.

Coatis Nasua nasua from Brazilian Pantanal. Photo

Figure 11.5 Coatis Nasua nasua from Brazilian Pantanal. Photo: Rita de Cassia Bianchi.

Actually, 86 of 235 examined animals (36.6%) displayed positive T. cruzi hemocul- tures.19 Besides, coatis were demonstrated to be infected by and maintain DTUs TcI, TcII, and TcIII/TcIV in single or mixed infections.19,68 The monitoring of recaptured mammals showed that T. cruzi-infected coatis can present high and long-lasting parasitemias by TcI and TcII. Due to their high biomass and high relative abundance among mammalian species, coatis certainly play a role in the amplification and dispersal of the main T. cruzi subpopulations in this region, demonstrating that predator—prey links may be excellent mechanisms for T. cruzi transmission and perpetuation in the wild.66—68 In the Pantanal the presence of Didelphis spp., considered as the main reservoir host of Trypanosoma cruzi was only negligible. In fact in this area, coatis were acting as the main reservoir hosts. This finding reinforces the importance of not electing a priori any target species as a reservoir.

Domestic and wild felines are animals that are especially difficult to handle. Maybe that’s why studies of T. cruzi infection of this taxon are less frequent and that their role in the transmission cycle of T. cruzi is still a matter of debate. Moreover, felines have a combination of ecological characteristics that favor them to get infected by T. cruzi: they are predatory animals, use large life areas, and have abilities to explore the arboreal and terrestrial strata of various habitats. We examined by hemocultures and serological methods free ranging Leopardus pardalis (N = 33), Leopardus tigrinus (N = 2), Leopardus geoffroyi (N = 1), Felis yagouaroundi (N = 2), Puma concolor (N = 2), and wild Felis catus (N = 3), from

Cerrado, Atlantic Forest, Pampa, and Pantanal biomes. From these, seven (16%) were positive and displayed serological titers that ranged from 1/40 to 1/160. Two L. pardalis with serological title 1/160, from the Cerrado, had positive blood cultures that were characterized as DTU TcI.66 The felines participate in the T. cruzi transmission cycle, both near the houses and in the wild environment. Nevertheless, one of the points that still needs to be observed is the duration of the competence infective; i.e., the period of high parasitemia that is expressed by positive parasitological tests.

Species diet could be associated with T. cruzi infection rates, showing the importance of predator—prey links as an important mechanism for T. cruzi dispersion in the wild. Also, it became clear that the distinct Carnivore taxa play distinct roles in the ecology of T. cruzi. Musteloidea species demonstrated high infectivity competence since they consistently exhibit high parasitemias as expressed by positive hemocultures.66 The DTU TcIII was isolated from a ferret (Galictis vitatta) in the Atlantic Forest of Rio de Janeiro, Brazil.19 Moreover, the isolation of Trypanosoma cruzi Z3 (that includes TcIII and TcIV) was achieved from skunks (Conepatus chinga) from Argentina,69 and gray foxes (Urocyon cinereoargenteus) in Central America and southern United States.70

One of the little known aspects concerning wild mammal and parasite interaction refers to the evaluation of their health status. Such clinical evaluation of an animal that was just captured and is at the peak of its stress is probably misleading. Besides, very probably, wild mammals are parasitized by several other species of parasites that interact and result in distinct outcomes, in addition to the physiological changes such as the case of the physiological immunosuppression during pregnancy and distinct susceptibility according to age and stress during the breeding season. Very little is known about the energetic costs for an animal that can result in a pattern of infection that could characterize it as an amplifier or maintenance host. Actually, a promising approach to better understand the outcome of parasite—host interactions in free living specimens is the evaluation of hematological parameters.71

 
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