Anti-Toxoplasma gondii and anti-Neospora caninum antibodies in capybaras (Hydrochoerus hydrochaeris) from Itu Municipality, São Paulo

Anticorpos anti-Toxoplasma gondii e anti-Neospora caninum em capivaras (Hydrochoerus hydrochaeris) do Município de Itu, São Paulo

Abstract

Capybaras (Hydrochoerus hydrochaeris) are the largest rodents found in South America. The aim of the present study was to investigate the occurrence of anti-Toxoplasma gondii and anti-Neospora caninum antibodies in 170 free-living capybaras in a residential park area in Itu Municipality, São Paulo State, Brazil. Serum samples were tested by indirect fluorescent antibody test (IFAT) for T. gondii (IFAT ≥ 1:16) and N. caninum (IFAT ≥ 1:50). Among the 170 samples analyzed, 10% (17/170) and 0% (0/170) were seropositive for T. gondii and N. caninum, respectively. This study confirms the widespread presence of T. gondii and reinforces the role of capybaras in the life cycle of this parasite. Capybaras may not be important as intermediate hosts of N. caninum in the studied environment.

Keywords:
Toxoplasma gondii; Neospora caninum; Hydrochoerus hydrochaeris; capybaras; Brazil; IFAT

Resumo

As capivaras (Hydrochoerus hydrochaeris) são os maiores roedores encontrados na América do Sul. O objetivo do presente estudo foi investigar a ocorrência de anticorpos anti-Toxoplasma gondii e anti-Neospora caninum em 170 capivaras de vida livre, habitando em um condomínio fechado no Município de Itu, Estado de São Paulo, Brasil. Amostras de soro foram testadas por meio da Reação de Imunofluorescência Indireta (RIFI) para T. gondii (RIFI ≥ 1:16) e N. caninum (RIFI ≥ 1:50). Entre as 170 amostras analisadas, 10% (17/170) e 0% (0/170) foram positivas para T. gondii eN. caninum, respectivamente. O presente estudo confirma a ampla distribuição de T. gondii e reforça o papel das capivaras no ciclo biológico desse parasita. Provavelmente, as capivaras não têm um papel importante como hospedeiros intermediários de N. caninum no ambiente estudado.

Palavras-chave:
Toxoplasma gondii; Neospora caninum; Hydrochoerus hydrochaeris; capivaras; Brasil; RIFI

Toxoplasmosis and neosporosis are caused by obligate intracellular apicomplexan protozoa that are distributed worldwide. Toxoplasma gondii infects any species of homeothermic animal, including humans (DUBEY, 2010). Neospora caninum is also widely seroprevalent in numerous species of mammals and birds (DUBEY & SCHARES, 2011). Domestic and wild felids are the definitive hosts ofT. gondii, whereas the domestic dog and other canids are the definitive hosts of N. caninum. More studies are necessary to determine which species can maintain N. caninum in the wild.

The capybara (Hydrochoerus hydrochaeris) is the largest rodent in the world and is distributed throughout Latin and Central America, from Panama to Argentina. It is an herbivore with semiaquatic habitats (OJASTI, 1991). Both anti-T. gondii and anti-N. caninum antibodies have previously been described in wild capybaras that live in direct contact with wild and domestic animals in Brazil (CAÑON-FRANCO et al., 2003; YAI et al., 2008a, b;VALADAS et al., 2010; TRUPPEL et al., 2010b). The objective of the present study was to investigate the frequency of anti-T. gondii and anti-N. caninum antibodies in free-living capybaras that inhabit a residential park in Itu Municipality, State of São Paulo, southeastern Brazil. This residential park is located in an area of conserved forest of 484 ha, including four lakes and approximately 400 homes. The most likely contact of these capybaras in this habitat is with dogs and cats, mostly pets, but there is no estimation of their overall numbers in the park.

From December 2012 to May 2013, 170 capybaras (70 males, 84 females and 16 with no recorded sex) were collected in corrals according to Moreira et al. (2013). This capture was legally authorized by the Brazilian agency SISBIO (“Sistema de Autorização e Informação em Biodiversidade”) after a severe case of Brazilian Spotted Fever occurred in a child who was bitten by ticks in this locality in September 2012 (KRAWCZAK et al., 2014). The residential park culled its entire capybara population to reduce the Amblyomma cajennense population to minimal levels. Individual blood samples were collected and sent to the laboratory for multiple serological analyses. The sera obtained by centrifugation were stored at –20 °C until processing and were individually tested by indirect fluorescent antibody test (IFAT) for anti-T. gondii (CAMARGO, 1974) and anti-N. caninum (DUBEY et al., 1988) antibodies. For T. gondii, tachyzoites of the RH strain were used as the antigen, and the cutoff value was 1:16. For N. caninum, tachyzoites of the NC-1 strain were used as the antigen, and the cutoff value was 1:50. Capybara IgG antiserum was prepared in sheep by the Zoonosis Control Center of the city of São Paulo (CCZ) and was labeled with fluorescein isothiocyanate, as described by Camargo (1964)and Hudson & Hay (1976). After standardization, the conjugate was used at a 1:1500 dilution for both agents. Positive and negative control sera from previous studies (YAI et al., 2008a, b) were included in all tests. This work was authorized by the Environment State Secretary of the state of São Paulo (authorization no. 96/2012) and was approved by the Ethical Committee of Animal Use of the Faculty of Veterinary Medicine of the University of São Paulo (protocol No. 3104/2013).

Among the 170 samples analyzed, 10% (17/170) were positive for T. gondiiand featured the following titers: 16 in 1 (0.6%), 32 in 5 (2.9%), 64 in 9 (5.3%) and 128 in 2 (1.2%). Among the positive animals, 10.7% (9/84) were female, 8.6% (6/70) were male and one did not have a recorded sex. Regarding the age groups, 4.8% (3/62) of the seropositive animals were infants (≤ six months), 11.4% (4/35) were juvenile (> six ≤ 12 months) and 13.7% (10/73) were adults (> 12 months). None of the animals was seropositive for N. caninum.

Capybaras are large herbivorous animals; therefore, they likely become infected withT. gondii or N. caninum by ingesting oocysts excreted by felids or canids, respectively, which contaminate the environment in which they live. This is the first study on the detection of anti-T. gondiiand anti-N. caninum antibodies in capybaras from the Municipality of Itu, São Paulo State.

Only two investigations have been performed on anti-N. caninumantibodies in capybaras in Brazil. Valadas et al. (2010) found 3% (2/63) seropositivity in animals from São Paulo State. In the same state, Yai et al. (2008b) reported 9.4% (20/213); however, the authors reported no occurrence of anti-N. caninum antibodies in four of the 11 municipalities included in the investigation. Truppel et al. (2010a) reported the molecular detection of N. caninum in capybaras (6/26) from Paraná state, suggesting this host could be a natural reservoir. But, despite serological and molecular evidence, viable N. caninum has not been isolated from capybaras yet.

In contrast, high seropositivity has been observed for T. gondii in wild capybaras. In the state of São Paulo, Cañon-Franco et al. (2003) reported 69.8% (104/149) seroprevalence, and Yai et al. (2008a) reported 75% (48/64) seroprevalence in six municipalities. Truppel et al. (2010b) found 61.5% (16/26) in capybaras from a park in the city of Curitiba, Paraná state, in the south of Brazil. Moreover, Yai et al. (2008a)confirmed the viability and large distribution of T. gondii in capybara tissues; they succeeded in isolating the parasite from 90% (36/40) of the seropositive animals bioassayed in mice. The present paper does not corroborate these previous studies because a low occurrence of T. gondii was observed. This lower frequency of anti-T. gondii antibodies and the absence of anti-N. caninum antibodies may be explained by the different habitats of the capybaras studied. While the capybaras in previous studies lived in the wild and with free migration to other areas, the capybaras in the present study inhabited a residential park with fewer stray cats and dogs and, consequently, lived in an environment less contaminated with oocysts.

In conclusion, our findings reinforce the role of the capybaras in the life cycle of toxoplasmosis in Brazil, but their impact in urban or anthropized environments may be less important than in the sylvatic cycle and more studies are required to investigate the role of capybaras in the epidemiology of N. caninum.

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Publication Dates

• Publication in this collection
  11 Mar 2016
• Date of issue
  Jan-Mar 2016

History

• Received
  05 Apr 2015
• Accepted
  06 May 2015