Clinical-pathological alterations, serological and molecular diagnosis in dogs with suspected leptospirosis

Leptospirosis is a globally important zoonosis that causes death in humans and animals, especially unvaccinated dogs. Dogs are infected through contact with urine or water contaminated by pathogenic spirochaete bacteria of the genus Leptospira. This study aimed to assess the performance of two diagnostic tests in characterizing dogs with leptospirosis and associate it with the main clinical-pathological alterations in dogs with suspected infection. From September 2019 to September 2020, 24 dogs with suspected canine leptospirosis were treated at the Veterinary Hospital of the Federal University of Uberlandia (UFU). Complementary tests such as a complete blood count (CBC) and serum creatinine, ALT (alanine transaminase) and ALP (alkaline phosphatase) levels were prescribed. In order to confirm the leptospirosis diagnosis, serum and molecular tests were performed using the microscopic agglutination test (MAT) and real-time quantitative polymerase chain reaction (qPCR). Of the 24 suspected cases of canine leptospirosis, six (25%) were positive in the MAT and three (12.5%) in the qPCR, with one (4.17%) returning positive results in both diagnostic tests. Positive results were obtained for 8/24 (33.3%) for combined MAT + qPCR. The predominant reactive serogroups were Icterohaemorrhagiae (33.33%) and Djasiman (33.33%), followed by Ballum (16.60%). The sensitivity and specificity of the qPCR in relation to the gold standard test (MAT) were 16.7 and 88.9%, respectively. Changes were observed in serum levels of creatinine, urea and ALP in the group that tested positive (MAT/qPCR); however, only urea and ALP levels were high in the negative group. Comparison of biochemical parameters in the positive (MAT/qPCR) and negative groups showed no statistically significant difference between the elements assessed (p>0.05). It was concluded that in order to diagnose acute canine leptospirosis, veterinarians should combine the clinical-pathological findings with paired sample MAT and qPCR urine test results.