Diagnóstico molecular e frequência de anticorpos anti-Leishmania infantum chagasi em cães do município de Belém, Pará

Abstract

Visceral leishmaniasis is a disease whose etiological agent in Brazil is Leishmania infantum chagasi. Dogs are considered urban reservoirs of the disease, being an indicator of the human cases occurrence. The present study aimed to diagnose L. infantum chagasi infection in stray and owned dogs in Belém, Pará State, by polymerase chain reaction (PCR) and indirect immunofluorescence assay (IFA) using two different antigens. Venous blood samples from adult dogs, regardless of gender or breed, of different neighborhoods in Belém-PA, were collected in tubes with and without anticoagulant to obtain DNA and serum, respectively. These animals were divided into two groups: stray dogs captured by the Center for Zoonosis Control (Group A) and owned dogs (Group B). Sera were analyzed by IFA testing for IgG using two different antigens: 1) Bio-Manguinhos/Fiocruz antigen kit (Ag-PRO) containing promastigotes of Leishmania sp. (Complex Major-Like), 2) Instituto Evandro Chagas Antigen (Ag-AMA) consisting of amastigotes of L. infantum chagasi. The evaluation of the two antigens was performed considering positive the reactions above the 1:80 dilution. Already PCR was performed with DNA isolated from whole blood of animals and amplified with the primers RV1 and RV2. Of the 335 samples analyzed, 10.4% (35/335) were positive by IFA (Ag-PRO) and 0.9% (3/335) with the Ag-AMA. The distribution of positive samples is given as follows: Group A 14.8% (25/169) with Ag-PRO and 1.2% (2/169) with Ag-AMA; Group B 6% (10/166) with Ag-PRO and 0.6% (1/166) with Ag-AMA, being that all samples positive by IFA with Ag-AMA also reacted with Ag-PRO, and none of the samples detected DNA of L. infantum chagasi. The findings of this study indicate that Belém can still be considered non-endemic area for canine visceral leishmaniasis and the nature of the antigen influences the result of the IFA for the detection of anti-L. infantum chagasi antibodies in dogs, and the IFA using promastigotes of Leishmania major-like antigen should be used with caution as a confirmatory diagnostic on epidemiological studies in non-endemic areas.