Exposure of free-living jaguars to Toxoplasma gondii, Neospora caninum and Sarcocystis neurona in the Brazilian Pantanal

Exposição de onças-pintadas a Toxoplasma gondii, Neospora caninum e Sarcocystis neurona no Pantanal brasileiro

Abstracts

Toxoplasma gondii, Neospora caninum and Sarcocystis neurona are related apicomplexan parasites that cause reproductive and neurological disorders in a wide range of domestic and wild animals. In the present study, the immunofluorescence antibody test (IFAT) was used to investigate the presence of antibodies against T. gondii, N. caninum and S. neurona in the sera of 11 free-living jaguars (Panthera onca) in two protected areas in the Pantanal region of Mato Grosso state, Brazil. Ten jaguars (90.9%) showed seropositivity for T. gondii, eight (72.7%) for S. neurona, and seven (63.6%) for N. caninum antigens. Our findings reveal exposure of jaguars to these related coccidian parasites and circulation of these pathogens in this wild ecosystem. To the best of our knowledge, this is the first serological detection of N. caninum and S. neurona in free-living jaguars.

Panthera onca; antibodies; Toxoplasma gondii; Neospora caninum; Sarcocystis neurona; conservation unit

Toxoplasma gondii, Neospora caninum e Sarcocystis neurona são coccídios relacionados responsáveis por causar desordens reprodutivas e neurológicas em uma ampla variedade de animais domésticos e selvagens. No presente estudo, a Reação de Imunofluorescência Indireta (RIFI) foi utilizada para investigar a presença de anticorpos contra T. gondii, N. caninum e S.neurona em soros de 11 onças-pintadas de vida livre (Panthera onca), provenientes de duas áreas protegidas na região do Pantanal do Estado de Mato Grosso, Brasil. Dez (90,9%), sete (63,6%) e oito (72,7%) onças amostradas foram soropositivas para T. gondii, N. caninum e S. neurona, respectivamente. Os resultados indicam a exposição a esses coccídios relacionados entre as onças-pintadas e a circulação ambiental desses patógenos nesse ecossistema selvagem. Este é o primeiro relato da detecção sorológica de N. caninum e S. neurona em onças-pintadas de vida livre.

Panthera onca; anticorpos; Toxoplasma gondii; Neospora caninum; Sarcocystis neurona; unidade de conservação

The complex dynamic relationship between wildlife, humans and domestic animals at the boundaries of protected areas underscores the importance of adopting proper control measures to prevent the transmission of infectious or parasitic diseases from humans or domestic animals to wildlife. This concern has been growing in recent decades for reasons that include the conservation of threatened species and the increasing recognition of emerging zoonotic diseases (DASZAK et al., 2000). Serologic studies have revealed the occurrence of antibodies against some infectious diseases in wildlife. However, reports about the health status of free-living jaguars (Panthera onca), the largest felid in the Americas, are still scanty, notwithstanding their situation in different categories of risk as a result of anthropogenic activities throughout the Brazilian territory (MORATO et al., 2013). Knowledge about health parameters is essential for the construction and implementation of action plans for global wildlife conservation. In Brazil, jaguars can be found in five different biomes, and the Pantanal biome is considered an important area for long-term jaguar conservation.

Toxoplasma gondii, Neospora caninum and Sarcocystis neurona are related apicomplexan parasites responsible for causing reproductive and neurological disorders in a wide range of domestic and wild animals (KENNY et al., 2002; DUBEY et al., 2001a, 2003b, 2007). The domestic cat (Felis catus) is the definitive host of T. gondii, an intracellular protozoan of worldwide distribution, although neotropical felids are also recognized as definitive hosts (JEWELL et al., 1972), emphasizing the importance of wild felines in the epidemiology of the agent in environments where cats do not exist (RENDÓN-FRANCO et al., 2012). The presence of anti-T. gondii antibodies has been reported in felids and canids in Brazilian zoos (SILVA et al., 2001; MATTOS et al., 2008; ANDRÉ et al., 2010), including seropositive captive jaguars. On the other hand, studies of exposure to T. gondii in free-living jaguars are still scanty (FURTADO, 2010).

Neospora caninum is considered one of the most important causes of abortion in cattle and of neurological disease in dogs. Antibodies against N. caninum have been reported in several wild species, such as wild herbivores and canids (DUBEY et al., 1999c; CAÑON-FRANCO et al., 2004; VALADAS et al., 2010; ALMERÍA, 2013), which can establish a plausible sylvatic cycle of the parasite, since coyotes (Canis latrans), dingoes (C. lupus dingo) and gray wolves (C. lupus lupus) are definitive hosts, similarly to domestic dogs (MCALLISTER et al., 1998; GONDIM et al., 2004a; KING et al., 2010; DUBEY et al., 2011). The presence of anti-N. caninum antibodies in several free-living and captive wild feline species has also been reported worldwide (CHEADLE et al., 1999; FERROGLIO et al., 2003; SPENCER et al., 2003; SEDLÁK & BÁRTOVÁ, 2006; ANDRÉ et al., 2010), but no clinical cases resulting from this parasite infection have been described in naturally infected felids (ALMERÍA, 2013).

Sarcocystis neurona and Neospora spp. are the etiological agents of equine protozoal myeloencephalitis (EPM). Sarcocystis neurona is one of the most commonly diagnosed pathogens of neurological disorders in horses in North America (DUBEY et al., 2003a), and a high prevalence of antibodies has been reported in horses in Brazil, Argentina, and Costa Rica (DUBEY et al., 1999a, b; HOANE et al, 2006; DANGOUDOUBIYAM et al., 2011). Currently, the opossum (Didelphis virginiana) is the only known definitive host for S. neurona in the United States (DUBEY & LINDSAY, 1998), and Didelphis albiventris has been implicated as the definitive host for the transmission of S. neurona in South America (DUBEY et al., 2001b; HOANE et al., 2006). Serological and parasitological studies have found that cats are natural intermediate hosts of S. neurona (STANEK et al., 2003; MENESES, 2012). However, to the best of our knowledge, there are no reports of serological studies or any information of naturally occurring S. neurona antibodies in wild felids, including jaguars.

The objective of this study was to evaluate the exposure of free-living jaguars to T. gondii, N. caninum and S. neurona in two protected areas in the Pantanal ecosystem of Mato Grosso state, central-western region of Brazil.

The study sites were the Taiamã Ecological Station (TES) (16° 50′ 34.31″ S, 57° 35′ 03.70″ W) and the Pantanal Matogrossense National Park (PNPM) (17° 50′47. 33″ S, 57° 24′12.67″ W), two Conservation Units in the Pantanal wetlands of the state of Mato Grosso, Brazil, considered one of the world's largest floodplains (Figure 1). The animals were captured intentionally during the dry season because they are impossible to catch when Pantanal is flooded. Captures were authorized by the National System for Biodiversity Research – SISBIO, under permit nos. 30896-1 and 18699-1. All the jaguars were captured using foot snares (BALME et al., 2009), immobilized with a dosage of 10 mg/kg of tiletamine/zolazepam (Zoletil 100^®, Virbac SA, Carros-Cedex, France) for blood collection and clinical examination, and fitted with GPS/VHF/satellite radio-collars (Vectronic Aerospace GmbH, Germany and Followit, Stockholm, Sweden). After these procedures, all the animals were released at the same sites where they were captured. Blood samples were collected by femoral venipuncture and stored in Brazil's Biological Samples Bank at the National Research Center for the Conservation of Carnivorous Mammals (CENAP/ICMBio).

Figure 1.
Location of the two Conservation Units in the Brazilian Pantanal where this study was conducted.

The immunofluorescent antibody test (IFAT) was performed to detect serum antibodies (IgG) against T. gondii, N. caninum and S. neurona, using the following antigens: T. gondii RH strain tachyzoites, as described by Camargo (1964); tachyzoites of N. caninum NC-Bahia strain (GONDIM et al., 2001), as described by Dubey et al. (1988); and S. neurona SN37R strain (SOFALY et al., 2002), as described by Duarte et al. (2003). The cut-offs adopted were dilutions of 1:16, 1:25, 1:25 for T. gondii, N. caninum and S. neurona, respectively (RIVETTI et al., 2008; ANDRÉ et al., 2010; MENESES, 2012). Serum samples from domestic cats (Felis catus) were used as positive and negative controls, and a goat anti-cat immunoglobulin G (anti-IgG) labeled with fluorescein isothiocyanate was used as conjugate. The slides were examined using an epifluorescence microscope. The samples considered positive were subjected to a two-fold serial dilution to obtain the final titer.

Eleven jaguars (7 males/4 females) were captured between July 2010 and November 2012. In general, all the animals were in good overall health, except jaguar #1, which showed low body weight, dermatological signs of systemic disease, and died 45 days after capture. We were unable to determine the cause of death, or to correlate it with any of the infections examined in this study. The age of the animals was estimated based on tooth wear and color, and all animals were considered adults, with estimated ages ranging from 4 to 10 years.

The results of serological assay are presented in Table 1. Ten (90.9%), eight (72.7%) and seven (63.6%) jaguars were seropositive for T. gondii, S. neurona and N. caninum antigen by IFAT, respectively. Titers of antibodies ranged from the dilutions 1:256 to 1:8,192 for T. gondii, from 1:100 to 1:1,600 for N. caninum, and from 1:25 to 1:800 for S. neurona. Five animals were reactive to all the antigens.

Table 1.
Results of serological assay performed on blood sera of free-living jaguars (Panthera onca) from the Pantanal region of Mato Grosso, Brazil.

Jaguar	IFA serological endpoint titers against each antigen
	Toxoplasma gondii	Neospora caninum	Sarcocystis neurona
1	1:1,024	1:100	1:25
2	1:2,048	1:800	1:800
3	1:1,024	1:1,600	1:100
4	N	1:200	1:50
5	1:2,048	N	1:50
6	1:256	N	N
7	1:1,024	1:800	1:800
8	1:1,024	1:100	N
9	1:2,048	N	1:50
10	1:256	N	N
11	1:8,192	1:100	1:50

• N= negative; IFA= immunofluorescent antibody test.

This study showed, for the first time, the occurrence of antibodies against three of the most important coccidia for veterinary medicine in free-living jaguars captured in the Pantanal, an important biome of South America, which is characterized by an extraordinary abundance of wildlife. A high frequency of antibodies against all protozoans was detected by IFAT, indicating the existence of a sylvatic cycle in these areas, most likely as a consequence of frequent exposure to these parasites.

Studies have shown antibodies to or evidence of infection with T. gondii, N. caninum and S. neurona in wild and domestic animals around the world, most of which are also present in the Pantanal, such as capybara, deer, canids, primates, birds, marsupials, as well as domestic dogs, cats, horses and cattle (DUBEY et al., 1988, 1999a, c; ROSSANO et al., 2002; CAÑON-FRANCO et al., 2003, 2004; GENNARI et al., 2004; LEITE et al., 2008; ALMERÍA, 2013). These domestic species are raised on cattle ranches and in rural communities in the Pantanal region on lands adjoining protected areas. As jaguars are at the top of the food chain, these findings may suggest that parasite infections occur further down the food chain (STUART et al., 2013), and that the role of predator-prey sentinels can be considered. However, further investigations involving this carnivore's ecology and prevalence within different species must be conducted in order to clarify this issue.

The high frequency of jaguars seroreactive against T. gondii appears to be common in Brazil. Our findings are similar to those reported by Furtado (2010), who detected seropositivity in all free-living jaguars sampled in Southern Pantanal, also suggesting a widespread sylvatic cycle of toxoplasmosis, although no statistical differences were found between prevalence in protected and disturbed areas.

Jaguar #1 was found dead 45 days after capture (data not shown). This animal was captured in the vicinity of a house (<300 meters) where several domestic dogs and cats lived and where predation had been reported. This jaguar presented anti-T. gondii antibody titers of 1:1024, which were higher than antibody titers against N. caninum or S. neurona (T= 1:100 and 1:25, respectively). However, a conclusive diagnosis could not be reached, because histopathological and immunohistochemical postmortem data were not available due to the level of decomposition of the carcass.

The T. gondii titer of 1:8,192 detected in jaguar #11 suggests active infection, despite the absence of clinical signs during its period of capture. In this case, other factors correlated with clinical signs of infection, such as virulence and genetic diversity of T. gondii and host immune response (PENA et al., 2011; CAÑÓN-FRANCO et al., 2013), must be considered. Clinical toxoplasmosis is rarely observed in domestic and wild felids, but reports of toxoplasmosis in domesticated cheetahs (Acinonyx acinonyx), captive lions (Panthera leo), Siberian tiger (Panthera tigris altaica), and Pallas cat (Otocolobus manul) attest to the susceptibility of Felidae species to this agent (DORNY & FRANSEN, 1989; OCHOLI et al., 1989; KENNY et al., 2002; LLOYD & STIDWORTHY, 2007).

This is the first serological detection of antibodies to N. caninum in free-living jaguars. The prevalence in this study (63.6%) is higher than that reported for Brazilian wild captive and exotic felids (ANDRÉ et al., 2010) and for wild felids in protected areas in Kenya, East Africa (FERROGLIO et al., 2003). Jaguar #3 had been feeding on horses (data not shown) in a private reserve adjacent to the PMNP and presented the highest antibody titers for N. caninum (1:1; 600), in addition to antibody titers for T. gondii (1:1,024) and S. neurona (100). Therefore, this proximity to human dwellings likely reflects frequent contact with probable domestic or domesticated animal hosts, which may act as sources of infection for all the tested antigens. Other sources of N. caninum infection should be considered. Serosurveys conducted in Brazil have revealed the occurrence of antibodies against N. caninum in capybaras (Hydrochaeris hydrochaeris) (YAI et al., 2008; VALADAS et al., 2010) and in pampas-deer (Ozotoceros bezoarticus) (TIEMANN et al., 2005), which are species commonly found in this region of the Pantanal and are known prey of jaguars, making infected animals available through carnivorism in the sylvatic cycle of the parasite. Although felids probably act only as intermediate hosts in neosporosis (ALMERÍA, 2013), the role of this top predator in the life cycle of this parasite and the influence of N. caninum infection on the health status of jaguar populations remains undefined. Serological evidence of infection and isolation of N. caninum in several wild species, added to the evidence that the parasite can be transmitted between wildlife and domestic animals (GONDIM et al., 2004b), involve new issues related to the transmission cycle of the parasite and to preventive measures in conservation units and their surrounding areas.

To the best of our knowledge, this is also the first report of S. neurona antibodies in jaguars. In addition to domestic cats, other wild species such as nine-banded armadillos (Dasypus novemcinctus), raccoons (Procyon lotor), sea otters (Enhydra lutris), striped skunks (Mephitis mephitis) and birds (Molothrus ater) have been described as intermediate hosts of S. neurona (CHEADLE et al., 2001a, b; DUBEY et al., 2001c, d; MANSFIELD et al., 2008). The frequency of seroreactive jaguars found in this study is higher than that found in cats in the USA and Brazil (ROSSANO et al., 2002; STANEK et al., 2003; MENESES, 2012). Despite the paucity of studies focusing on the identification of natural intermediate hosts in South America, there are Procyonidae and Edentate species in Brazil which can be infected with S. neurona and which have been shown to be intermediate hosts for this agent in North America (CHEADLE et al., 2001a; HOANE et al., 2006). These species may play an important role in the natural maintenance of this parasite in this region, but there are no reports of anti-S. neurona antibodies in wild felid species, and little information about S. neurona infection in cats is available in Brazil. Despite the suggested participation of domestic and feral cats in the epidemiology of MPE in ecological niches shared with marsupials and other intermediate hosts (STANEK et al., 2003), predatory species do not often serve as intermediate hosts for many of the parasitic life cycles (STANEK et al., 2003), and studies are needed to clarify the role of jaguars in the life cycle of this agent.

The lack of reports of clinical signs of T. gondii, N. caninum and S. neurona infection in jaguars in natural environments prevent a clear understanding of the potential impact on this species of conservation concern, despite evidence of the influence of parasitic infections in birth and death rates, even when clinical signs are not obvious (TELFER et al., 2008). A better understanding is needed of environmental contamination by oocysts and of transmission mechanisms in flooded areas such as the Pantanal ecosystem, in view of their public health, economic and biodiversity implications. Whenever possible, diagnostic techniques such as histopathology, immunohistochemistry and molecular analysis associated with serological data would be useful to clarify the real participation of this species in the epidemiology of T. gondii, N. caninum and S. neurona.

Acknowledgements

We are indebted to the researchers of the Laboratory of Virology and Rickettsiosis of UFMT for their technical support. This work was supported by CNPq (National Council for Scientific and Technological Development) through a research grant and scholarship for DMA, and by CAPES (Federal Agency for the Support and Improvement of Higher Education) through a scholarship granted to ALTM. We also thank the National Research Center for the Conservation of Carnivorous Mammals (CENAP/ICMBio) for its financial and technical support of the animal captures.

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Publication Dates

• Publication in this collection
  Dec 2014

History

• Received
  16 June 2014
• Accepted
  4 Aug 2014