AVALIAÇÃO DO DESEMPENHO DIAGNÓSTICO DE NOVAS TÉCNICAS SOROLÓGICAS PARA LEISHMANIOSE VISCERAL CANINA

Abstract

Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum. Dogs are considered important urban reservoir for the parasite and canine visceral leishmaniasis (CVL) diagnosis contributes for monitoring and reemergence of VL. CVL confirmatory diagnosis as recommended by the Mistry of Health is performed using enzyme-linked immunosorbent assay (ELISA) with crude antigen of L. major-like. However, this technique may provide false positive results for animals infected with other trypanosomatids or Ehrlichia canis. Besides that, false negative results may be obtained for asymptomatic dogs, which can act as the parasite reservoir in the urban environment. In this context, recombinant antigens have been developed individually or combined to increase sensitivity, specificity, and accuracy of CVL serodiagnosis. This study analyzed three serologic tests for CVL diagnosis: two national developed ELISA using recombinant proteins (Q1 and Q5) and one rapid test using antigen of L. donovani promastigote membrane, in dipstick presentation. To evaluate chimeric proteins performances in ELISA, samples from a serological bank were used. Samples from naturally infected dogs with L. infantum symptomatic (n=30), oligosymptomatic (n=30) and asymptomatic (n=10); healthy (n=30), vaccinated with Leish-Tec (n=5) and Leishmune  (n=5) and infected with E. canis (n=30) were used. The performance of chimeric ELISAs were compared to the ELISA with L. infantum total extract as antigen. Greater values of sensitivity and specificity were observed, respectively, for Q1 (81.43%; 85.71%) and Q5 (74.29%; 90.0%), when compared to total extract antigen (71.43%; 82.86%). Although Q1 presented cross-reaction with Leish-Tec-vaccinated dogs, this chimeric protein demonstrated better sensitivity to diagnose asymptomatic (70%) and oligosymptomatic (73,33%) dogs. To access dipstick performance, samples from naturally infected dogs with L. infantum symptomatic (n=15), oligosymptomatic (n=15) and asymptomatic (n=9); healthy (n=15); vaccinated with Leish-Tec (n=5) and infected with E. canis (n=15) were obtained from a sera bank. The dipstick test presented higher sensitivity in the oligosymptomatic group (93.33%); followed by asymptomatic (77.88%) and symptomatic (73.33%); specificity value of 100% was observed for the test among all groups. Therefore, Q5 may be an interesting antigen for the development of serological tests and dipstick test could be a useful tool for CVL diagnosis due to its ease of performance. Both methods demonstrated good performance in situations where canine ehrlichiosis may be a differential diagnosis for the patient.