Chagas Immunochromatographic Rapid Test in the Serological Diagnosis of Trypanosoma cruzi Infection in Wild and Domestic Canids

Abstract

<i>Canis lupus familiaris</i> (domestic dog) represents a reliable sentinel for the occurrence of a well-established transmission cycle of <i>Trypanosoma cruzi</i> among wild mammals in the surroundings and, consequently, where the risk of human infection exists. Serological diagnosis is the chosen method to identify <i>T. cruzi</i> infection in dogs that, in Brazil, rarely present positive parasitological tests. The use of recombinant chimeric parasitic antigens results in a sensitive and specific serological diagnostic test in contrast to the use of crude <i>T. cruzi</i> antigens. Our objective was to evaluate the Chagas/Bio-Manguinhos Lateral Flow Immunochromatographic Rapid Test (Chagas-LFRT) for the diagnosis of <i>T. cruzi</i> infection in domestic dogs and the potential of application of this diagnostic platform to wild canid species. Two recombinant proteins (IBMP-8.1 and IBMP-8.4) that displayed the best performance in the enzyme immunoassay (ELISA) in previous studies were tested in a platform with two diagnostic bands. A panel of 281 dog serum samples was evaluated: 133 positive for <i>T. cruzi</i> by serological diagnosis, including 20 samples with positive blood cultures belonging to different discrete typing units (DTUs); 129 negative samples; and 19 samples from dogs infected by other trypanosomatids: <i>Leishmania infantum</i>, <i>Trypanosoma rangeli</i>, <i>Trypanosoma caninum</i> and <i>Crithidia mellificae</i>, in addition to samples infected by <i>Anaplasma platys</i>, <i>Dirofilaria immitis</i> and <i>Erlichia</i> sp. that were employed to evaluate eventual cross-reactions. We also evaluated the Chagas-LFRT to detect <i>T. cruzi</i> infection in 9 serum samples from six wild canid species. We observed that the intensity pattern of the bands was directly proportional to the serological titer observed in IFAT. The sensitivity was 94%, the specificity was 91% according to the ROC curve, and the defined cutoff was an optical density of 4.8. The agreement obtained was considered substantial by the kappa analysis (84%). From <i>T. cruzi</i> positive hemoculture samples, 88.9% were positive by Chagas-LFRT. The test was efficient in recognizing infections by five of the six <i>T. cruzi</i> DTUs. Cross-reactions were not observed in infections by <i>L. infantum</i>, <i>T. rangeli</i>, <i>T. caninum</i> and <i>D. immitis</i>; however, they were observed in sera of dogs infected by <i>Crithidia mellificae</i>, <i>Anaplasma</i> sp. and <i>Erlichia</i> sp. A strong reaction was observed when serum samples from wild canids were submitted to the Protein A affinity test, confirming its applicability for these species. This test will allow rapid preventive actions in areas with high risk to the emergence of Chagas disease in a safer, reliable, low-cost and immediate manner, without the need for more complex laboratory tests.