Diagnosis of Leishmania infantum infection by Polymerase Chain Reaction in wild mammals

Diagnóstico de infecção por Leishmania infantum pela reação em cadeia da polimerase em mamíferos silvestres

ANIMAIS SELVAGENS/WILDLIFE MEDICINE

Diagnosis of Leishmania infantum infection by Polymerase Chain Reaction in wild mammals

Diagnóstico de infecção por Leishmania infantum pela reação em cadeia da polimerase em mamíferos silvestres

Mayara C. Lombardi^I; Andréia P. Turchetti^I; Herlandes P. Tinoco^II; Angela T. Pessanha^II; Semiramis A. Soave^II; Marcelo C.C. Malta^II; Tatiane A. Paixão^III; Renato L. Santos^I*

^IDepartamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, MG 31270-901, Brazil. E-mails: [e-mail], [e-mail] ^IIFundação Zoo-Botânica, Av. Otacílio Negrão de Lima 8000, Belo Horizonte, MG 31365-450. E-mails: [e-mail], [e-mail], [e-mail], [e-mail] ^IIIDepartamento de Patologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, MG 31270-901. E-mail: tatipaixã[e-mail]

ABSTRACT

Visceral leishmaniasis is a chronic infectious disease caused by Leishmania infantum (synonym: Leishmania chagasi) and transmitted by the sandfly Lutzomyia longipalpis in Brazil. It is an endemic zoonosis in several regions of the country, including Belo Horizonte (State of Minas Gerais). In urban areas, the domestic dog is susceptible and considered the most important animal reservoir. However, L. infantum has been previously diagnosed in other species, including captive primates and canids. This study aimed to evaluate the presence of the agent DNA in captive animals as well as some free ranging animals from the Zoo-Botanical Foundation of Belo Horizonte by Polymerase Chain Reaction. Eighty one blood samples from primates, carnivores, ruminants, edentates, marsupial, and a monogastric herbivore were analyzed. Three primates Alouatta guariba (brown howler monkey), and two canids Speothos venaticus (bush dog) were positive, demonstrating the importance of leishmaniasis control in endemic areas for preservation of wildlife species in captivity.

Index terms: Leishmaniasis, Leishmania infantum, zoo, visceral leishmaniasis, PCR.

RESUMO

A leishmaniose visceral é uma doença infecciosa crônica de mamíferos causada, no Brasil, pelo protozoário Leishmania infantum (sinonímia: Leishmania chagasi) e transmitida pelo flebótomo Lutzomyia longipalpis. Trata-se de uma zoonose endêmica em muitas regiões do Brasil, inclusive em Belo Horizonte, Minas Gerais. Em centros urbanos, leishmaniose visceral acomete principalmente o cão doméstico. Entretanto, L. infantum já foi diagnosticada em outras espécies, incluindo canídeos e primatas de cativeiro em zoológicos. Este estudo buscou avaliar a presença do DNA deste agente em animais de cativeiro e de vida livre da Fundação Zoobotânica de Belo Horizonte através da reação em cadeia da polimerase. Foram analisadas oitenta e uma amostras de sangue oriundas de primatas, carnívoros, ruminantes, edentatos, marsupial e herbívoro de estômago simples. Três primatas Alouatta guariba (bugio marrom) e dois canídeos Speothos venaticus (cachorro-do-mato-vinagre), foram positivos, demonstrando a importância do controle da leishmaniose em áreas endêmicas com a finalidade de conservar a fauna silvestre mantida em cativeiro.

Termos de Indexação: Leishmaniose, Leishmaniainfantum, zoológico, leishmaniose visceral, PCR.

INTRODUCTION

Visceral leishmaniasis (VL) is an important zoonosis characterized by a chronic systemic disease. In Brazil, VL is caused by Leishmania infantum (synonym: Leishmania chagasi). Its definitive hosts are mammals, mainly domestic dogs (Canis familiaris) that play a major epidemiological role in urban areas, where it is considered the most important reservoir for human infections (Diniz et al. 2008). Dogs are in close contact with humans and they may be asymptomatic, which increases the risk of transmission. VL is endemic in Belo Horizonte, where it has become a major public health issue (Diniz et al. 2008). Although transmission may occur in the absence of the biological vector (Pangrazio et al. 2009, Silva et al. 2009), usually Leishmania spp. is transmitted by an invertebrate vector, which in the case of L. infantum in Brazil is the sand fly Lutzomyia longipalpis (Rosypal et al. 2003), which is abundant in the metropolitan area of Belo Horizonte (Resende et al. 2006).

L. infantum infection has also been detected in wildlife species in Brazil, including canids (Figueiredo et al. 2008, Luppi et al. 2008, Souza et al. 2010), primates (Malta et al. 2010), and felids (Dahroug et al. 2010). The role of these species as reservoirs is unclear, but some species are susceptible to clinical development of the disease (Luppi et al. 2008, Malta et al. 2010). Furthermore, L. infantum has been detected in other groups of wild mammals that are present in urban areas in Brazil, including rodents (Oliveira et al. 2005) and marsupials (Schallig et al. 2007, Santiago et al., 2007) that may also function as potential reservoirs. Leishmaniasis affecting zoo and wildlife has been recently reviewed (Souza et al., 2014).

This study aims to investigate the presence of the L. infantum DNA by PCR (Polymerase Chain Reaction) in blood samples from several captive and free-ranging mammal species potentially susceptible to infection at the Zoo-Botanical Foundation of Belo Horizonte (ZBF-BH).

MATERIALS AND METHODS

From April 2011 to August 2012, 81 blood samples were collected from captive or free-ranging wild mammals that underwent medical procedures at the veterinary hospital from the ZBF-BH. A total of 81 blood samples were analyzed: 26 samples from primates, 26 from carnivores (including 14 felids, 10 canids, and 2 mustelids), 10 from edentates, 9 from ruminants, 8 from rodents, 1 from a marsupial, and 1 from a monogastric herbivore. Blood samples were collected into EDTA sterile tubes and kept refrigerated at 4^oC. Blood samples were centrifuged at 1500 g for 10 minutes to separate the buffy coat and extract its DNA by the guanidine method (Pitcher, Saunders and Owen 1989). DNA concentrations were measured and adjusted to 100-500ng/μL. PCR was performed according to Lachaud et al. (2002) to amplify minicircles of kinetoplast DNA from Leishmania spp. belonging to the donovani complex using 23μL of PCR Supermix (Invitrogen, Brazil), 0.5μL of 10μM sense primer (5’- CTT TTC TGG TCC CGC GGG TAGG -3’), 0.5μL of 10μM antisense primer (5’- CCA CCT GGC CTA TTT TAC ACCA -3’), 0.7μL of MgCl₂, 0.2μL of Taq Polymerase (Invitrogen, Brazil) and 1μL of extracted DNA (100-500ng/μL). PCR products were visualized under UV light after electrophoresis in a 2% agarose gel stained with ethidium bromide. Samples that yielded a 145 bp product were considered positive. Positive and negative controls were included in all reactions.

RESULTS

PCR results and detailed species identification and their respective numbers are shown in Table 1.

Five samples, three from Alouatta guariba (brown howler monkey) and two from Speothos venaticus (bush dog), were positive for leishmanial DNA (Table 1). Therefore, only one primate and one carnivore species were PCR-positive for Leishmania infantum. The remaining 10 primate species, seven carnivore species, two edentate species, five ruminant species, three rodent species, one marsupial species, and one monogastric herbivore species were all negative by PCR (Table 1).

DISCUSSION

Among eleven different primate species that were sampled, all three positive animals belonged to the same species, namely Alouatta guariba (brown howler monkey). Leishmania sp. has been previously detected by PCR in the peripheral blood of this species (Malta et al. 2010). Anti-L. mexicana IgG antibodies have been detected in two species of the Alouatta genus, i.e. A. pigra and A. palliate, in Mexico (Rovirosa-Hernandez et al. 2013). Leishmaniasis affecting zoo and wildlife species have been recently reviewed (Souza et al., 2014).

Among the carnivore species sampled in this study, only two bush dogs (Speothos venaticus) were positive. The bush dog is known to be susceptible to Leishmania infantum since previous studies have reported direct detection the agent (Figueiredo et al. 2008, Luppi et al. 2008, Lima et al. 2009, Souza et al. 2010) or detection of anti-Leishmania antibodies (Lima et al. 2009, Jusi et al. 2011) in various biological samples. Considering that this is an endangered species according to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES - www.cites.org), prevention and control of L. infantum infection in captive specimens is extremely important for conservation purposes. Therefore, epidemiological studies, clinical monitoring, and L. longipalpis control are extremely important measures in zoos located in endemic areas as is the case of ZBF-BH. The significance of wild canids in the pathobiology of leishmaniasis is reflected by the large number of recent publications on this topic, which includes the report of three wolves (Canis lupus) out of 33 sampled in Southwestern Europe that were positive to L. infantum by PCR (Sastre et al. 2008). In addition, Sobrino et al. (2008) detected L. infantum by PCR in eight of 39 wolves, 23 of 162 foxes (Vulpes vulpes) in Spain, whereas Dipineto et al (2007) detected the parasite from 20 of 50 fox carcasses in Italy. Antibodies against Leishmania spp. were found in one gray fox (Urocyon cinereoargenteus) from the United States, out of 49 sampled (Rosypal et al. 2010). In Brazil, Leishmania sp. has been reported in both free-ranging and captive canids. In the State of Minas Gerais, antibodies against Leishmania sp. have been detected in hoary zorros (Lycalopex vetulus) (Luppi et al. 2008), crab-eating foxes (Cerdocyon thous) (Curi et al. 2006, Luppi et al. 2008) and maned wolves (Chrysocyon brachyurus) (Curi et al. 2006, Luppi et al. 2008, Curi et al. 2012). In São Paulo State, in addition to the bush dog and maned wolf, Leishmania spp. was detected in the crab-eating fox through different techniques such as ELISA, PCR and indirect fluorescent antibody test (IFAT) (Jusi et al. 2011). L. infantum was also detected in skin, bone marrow and lymph node samples by PCR from six crab-eating foxes and one bush dog in state of Mato Grosso (Souza et al. 2010). Furthermore, L. infantum has been detected in wild felids such as two captive barbary lions (Panthera leo leo) in France (Libert et al. 2012), one genet (Geneta geneta) and one Iberian lynxes (Lynx pardinus) in Spain (Sobrino et al. 2008). In Brazil, it was detected in five captive cougars (Puma concolor) and in one captive jaguar (Panthera onca) in state of Mato Grosso (Dahroug et al. 2010).

Importantly, none of the edentates, ruminants, rodents, marsupial, and monogastric herbivore sampled in this study were positive. However, some species belonging to these groups had been previously diagnosed with Leishmania sp. and, therefore, they may be considered potential reservoirs. Indeed, Leishmania sp. infection in opossums has been detected by PCR in 91.6% of 112 sampled Didelphis spp. from São Paulo State, and, among these, 71% had anti-Leishmania antibodies (Santiago et al. 2007). In a similar study performed in Minas Gerais, five of 20 Didelphis marsupialis were PCR positive for Leishmania sp., and 24 out of 111 were positive by IFAT (Schallig et al. 2007). L. infantum DNA was detected by PCR in 15 out of 54 Didelphis albiventris opossums in the State of Mato Grosso do Sul, Brazil (Humberg et al. 2012). Leishmania sp. was also detected by PCR in three rodent species, Rattus rattus, Thrichomys apereoides, and Oryzomys subflavus in Brazil (Oliveira et al. 2005), and Rattus norvegicus in Greece (Papadogiannakis et al. 2010). In Spain, Lepus granatensis were reported to be infected with L. infantum, and they were capable of infecting sandflies as confirmed by xenodiagnosis (Molina et al. 2012).

Not much is known about the Leishmania sp. cycle in wild animals. Theoretically, exposed animals might be resistant and overcome the parasite; alternatively some host species might allow the protozoa to multiply but not develop disease, being able to transmit amastigotes to the sandfly and thus contribute to the transmission of the disease; whereas other host species might be susceptible, develop disease and also contribute to the dissemination of leishmaniasis. PCR results, which detect only the presence of the parasite DNA, should be analyzed carefully, as it is an extremely sensible test able to detect low concentrations of Leishmania DNA, what does not necessarily indicate persistent infection or disease. However, these results are relevant since it clearly indicates exposition of captive wild animals to the parasite. In addition, Luppi et al. (2008) reported previously a case of a captive brush dog from the Zoo-Botanical Foundation of Belo Horizonte (ZBF-BH) that died due to clinical VL. The animal presented cachexia, anemia, generalized hemorrhage and chronic renal failure. L. infantum was detected by immunohistochemistry and PCR. A crab-eating fox from São Paulo State, Brazil, also died due to VL. The diagnosis was confirmed by IFAT, PCR and direct observation of amastigotes in macrophages from liver, spleen, lymph nodes and skin (Tenório et al. 2011). Malta et al. (2010) reported a case of confirmed clinical leishmaniasis in a black-fronted titi monkey (Callicebus nigrifrons) also from ZBF-BH.

Although blood may not be considered the biological sample of choice for the diagnosis of Leishmania sp. infection, the method used in this study is highly sensitive since it amplifies a sequence of the kDNA minicircle that has multiple copies, which increases the sensitivity of the method (Lachaud et al., 2002). Importantly, even with blood samples, PCR is a suitable method for diagnosis of Leishmania sp. infection when compared to other methods (Assis et al., 2010). Finally, in this study, serological methods could not be applied due to the variability of species included in this survey. Furthermore, the use of additional biological samples, such as bone marrow or lymph node aspirates is not feasible due to limitations to manipulate these animals.

CONCLUSION

Leishmania infantum DNA was detected in five out of the 81 blood samples from wild mammals of the ZBF-BH, three positive samples were from Alouatta guariba and two from Speothos venaticus.

ACKNOWLEDGEMENTS

Work in RLS lab is supported by CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) and FAPEMIG (Fundação de Amparo a Pesquisa do Estado de Minas Gerais).

Received on June 30, 2014

Accepted for publication on October 20, 2014

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Publication Dates

• Publication in this collection
  29 Jan 2015
• Date of issue
  Dec 2014

History

• Received
  30 June 2014
• Accepted
  20 Oct 2014