Canine visceral leishmaniasis diagnosis: a comparative performance of serological and molecular tests in symptomatic and asymptomatic dogs.

Although serological assays have been widely used for the diagnosis of canine visceral leishmaniasis (CVL), they present different performances depending on the clinical profile of the dogs. This study evaluated the accuracy of serological tests, immunochromatographic (Dual Path Platform: DPP®) and enzyme-linked immunosorbent (ELISA EIE®), for CVL in relation to the detection of Leishmania DNA through real-time polymerase chain reaction (real-time PCR) in samples from symptomatic and asymptomatic dogs from a non-endemic area in the state of Rio Grande do Sul, Southern Brazil. Serum from 140 dogs (39 symptomatic and 101 asymptomatic) was tested by DPP and ELISA followed by real-time PCR. From a total of 140 samples evaluated, Leishmania DNA was detected by real-time PCR in 41.4% (58/140). Moreover, 67.2% of samples positive in real-time PCR were positive in both DPP and ELISA (39/58), showing moderate agreement between methods. In the symptomatic group, one sample non-reactive in both serological assays was positive in real-time PCR, whereas in the asymptomatic group, 17.8% non-reactive or undetermined samples in serological assays were positive in the molecular method. Leishmania DNA was not detected in 17.9% reactive samples by serological assays from the symptomatic group, and in 3.9% from asymptomatic dogs. Real-time PCR demonstrated greater homogeneity between symptomatic and asymptomatic groups compared with DPP and ELISA. The molecular method can help to establish the correct CVL diagnosis, particularly in asymptomatic dogs, avoiding undesirable euthanasia.