versão On-line ISSN 1678-4162
Arq. Bras. Med. Vet. Zootec. v.54 n.4 Belo Horizonte jul./ago. 2002
Serological surveillance on South American wild canids for Neospora caninum
[Sorologia para Neospora caninum em canídeos silvestres sul-americanos]
C.B. Melo1,3*, R.C. Leite2,3, F.S.C. Leite4, R.C. Leite2,3
1 DEA / CCBS / UFS Cidade Universitária Prof. José Aloísio de Campos - Jardim Rosa Elze
49100-000 São Cristóvão, SE
2 Escola de Veterinária da UFMG
3 Bolsista do CNPq
4 Faculdade de Medicina da UFMG. Bolsista da FAPEMIG
Recebido para publicação em 9 de julho de 2001
Recebido para publicação, após modificações, em 15 de abril de 2002
Neospora caninum (Apicomplexa, Toxoplasmatinae) is a protozoan recently described infecting canids that show similar symptomatology to those infected with Toxoplasma gondii (Dubey et al., 1988). In naturally infected canids, neurological problems, polimyositis, myocarditis, ulcerated and piogranulomatous dermatitis and generalized disease have been reported (Dubey et al., 1988; Dubey et al., 1995; Barber & Trees, 1996). Canines are not only the intermediate host (Wouda et al., 1999; Mineo et al., 2001), but they have also been reported as the parasite's final host (McAllister et al., 1998; Lindsay et al., 1999). Sheep, goats, cattle, buffaloes and horses are naturally exposed to infection and other species as monkeys, gerbils, rats, mice and pigs were successfully experimentally infected by N. caninum (Dubey, 1999). The parasite is distributed worldwide (Dubey, 1999).
Neospora caninum has been studied in savage animals, especially canids, with the aim to identify wild populations in which the parasite may occur and to show the importance of these species may have as hosts in the parasite's life cycle. Among those, the coyote, Canis latrans (Lindsay et al., 1996), the Australian dingo, C. familiaris dingo (Barber et al., 1997), the red fox, Vulpes vulpes (Barber et al., 1997; Buxton et al., 1997; Simpson et al., 1997), the gray fox, Urocyon cinereoargenteus (Lindsay et al., 2001), were reported to be very susceptible to the parasite. The exposure of maned wolves, Chrysocyon brachyurus (Illiger, 1811) and crab-eating fox, Cerdocyon thous (Linnaeus, 1758) to N. caninum is not known. This report aim to survey IgG antibodies to N. caninum in maned wolves and crab-eating fox, both wild or raised in zoo.
Blood samples were collected by cephalic or jugular vein punctures from 48 maned wolves and from two crab-eating foxes, according to a license issued by the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA). The samples from wolves were collected during 1997 in several Brazilian zoos and free-ranging animals (Tab.1). All four free-ranging wolves captured were less than one-year-old while the others that came from zoos ranged from various ages. The samples from crab-eating foxes (two adult females) were collected in 2000 (november) in IBAMA headquarter in Belo Horizonte, State of Minas Gerais. The samples from maned wolves and crab-eating foxes were collected and stored at 20 oC until use.
The samples were tested individually, at room temperature, for the presence of IgG using a commercial indirect immunofluorescence test (VMRD Pullman/USA.). Positive and negative control samples were from dogs (VMRD). IgG polyclonal anti-serum anti-canids was produced in goats and conjugated with fluoresceine isotiocyanate (VMRD). Tests were carried out following producers recommendations and the samples were tested diluted at 1:50 in 12 wells plates filled with tachyzoites, grown in VERO cells and fixed on teflon surface. After reactions ended, glycerol was added, the samples covered with coverslips and the reading was carried out immediately using ultra-violet emission microscope (Olympus CBA, Japan.) with 250X magnification and confirmed at 400X magnification. Samples were analyzed for tachyzoites fluorescence homogeneity.
Specific fluorescence for N. caninum was not seen in any of the tested samples. Therefore it was not possible to confirm evidence of infection of N. caninum. Considering that control samples for N. caninum on the species studied are not available, it was decided to use positive and negative serum samples from dogs. In all plates, one well was filled with positive serum dog sample that showed complete peripheral tachyzoite fluorescence. Apical fluorescence (non specific) was not considered positivity evidence due to possible cross-reaction with other parasites (Paré et al., 1995).
The natural presence of antibodies to N. caninum in dogs has been reported with variable prevalence. McAllister et al. (1998) and Lindsay et al. (1999) showed that, although having negative immunofluorescence test results, some dogs experimentally infected showed the presence of N. caninum oocysts on their stools. Wild mammal populations, especially canids, have not been properly tested to evaluate whether they are definitive hosts to N. caninum (McAllister et al., 1999).
Maned wolf is the biggest canid in South America, specially in Brazilian savannah, but it may also be seen in higher lands and swamp areas. Its behavior is different from other canids due to its nocturnal practices and opportunistic alimentation: omnivorous, seasonal, mainly consisting of small rodents, birds and wild fruits. International institutions such as "The World Conservation Union" (IUCN) and "II Convention on International Trade in Endangered Species of Wild Fauna and Flora"classify this species as being under extinction risk. In Brazil it is officially considered an endangered species since 1989 and in Minas Gerais it is mentioned in the endangered list of species possibly extinct on medium terms (Maia et al., 1999).
Crab-eating fox inhabits fields and savannahs in almost all South America countries, including Brazil, and it is the main naturally occurring canid in the continent. It has nocturnal habits and lives alone or in pairs. Its alimentation depends on the season and in Venezuela it was shown to consist, during the rainy season, of 54% insects and 20% vertebrates and, during the dry season, of 48% vertebrates, 31% crabs and 16% insects (Fundação Zoobotânica de Belo Horizonte, November, 15, 2001. http://www.pbh.gov.br/zoobotanica/zoo/mamifero/cach_mato.htm). Despite the fact of not being classified as immediate-protection-requiring endangered species by IUCN/SSC by canid specialist group, in 1990, which means that it is not on extinction hazard yet (The World Conservation Union (IUCN). November, 17, 2001. http://www.canids.org/1990cap/conclusn.htm#crabfox), it has been protected by Brazilian environmental legislation (IBAMA) because it is part of the Brazilian fauna.
The species studied are omnivorous and their alimentation varies according to season and prey availability. Thus, the exposure to N. caninum may be relevant. Besides, their sensitivity to the parasite is not known. They probably show low or even no prevalence at all of N. caninum infection. Maned wolf and crab-eating fox relations to N. caninum need further studies, specially the first one, which is an endangered species and highly susceptible to common dogs pathogens, such as canine distemper virus (Cabasso et al. 1956), which causes neurological disorders, mortality and must be considered in a differential diagnosis of neosporosis. Their habitat destruction has great consequences, such as a closer contact to dogs in rural areas, increasing the exposure to dog pathogens. Other parasite infective stages were not studied and therefore those canids cannot be disregarded of epidemiological importance in the parasite's life cycle. They might be natural reservoirs that keep infection in nature.
According to the tests performed, maned wolf and crab-eating foxes studied were not exposed to infection by N. caninum. Nevertheless, the number of samples was very small and infection may be underestimated, not showing the precise relation between those two species and N. caninum. The specificity and sensitivity of the immunofluoresce test used were not evaluated for those canids, and these results must be interpreted cautiously.
Keywords: Maned wolf, crab-eating fox, Neospora caninum
This research was supported by FEP - MVZ Coordenação Preventiva (UFMG) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). We thank to Carlos Wilson Gomes Lopes and Luis Fernando Pita Gondim for their suggestions regarding to the manuscript. We also thank Aryane Machado Siqueira (IBAMA Minas Gerais), for cooperation and allowance to work with crab-eating foxes and to Otávio Borges Maia, for supplying the maned wolfs' samples.
Esse trabalho objetivou pesquisar anticorpos para Neospora caninum em amostras de soro de canídeos silvestres sul-americanos pela técnica de imunofluorescência indireta (IFI). As amostras foram coletadas de 48 lobos-guará (Chrysocyon brachyurus), provenientes de zoológicos e de vida livre e de dois cachorros-do-mato (Cerdocyon thous). Anticorpos para N. caninum não foram detectados nas amostras testadas.
Palavras-chave:Lobo-guará, cachorro-do-mato, Neospora caninum.
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