Detection of Pathogenic Leptospiral DNA Traces in Canine Sera Serum Samples by Loop Mediated Isothermal Amplification (LAMP)

Leptospirosis is a worldwide distributed zoonosis, caused by pathogenic strains of spirochetes belonging to the genus Leptospira spp. So far, the only gold standard diagnostic method for this disease has been the Micro-Agglutination Test (MAT). The purpose of this study was to test whether a correlation exists between serological diagnosis by MAT and the presence of Leptospira spp. DNA traces in serum. Anti-Leptospira spp. antibody titers were determined in dog serum samples obtained at a canine shelter from Buenos Aires Province, Argentina (n= 80) by MAT using ten Leptospira spp. serovars. DNA extracted from these samples using Chelex-100 resin was used as template for Leptospira spp. specific PCR and loop-mediated isothermal amplification (LAMP) tests. In the latter case, product detection by incubation with malachite green dye was set up, obtaining optimal results at a dye concentration of 0.02% (w(v)) and a pH of 6.1. PCR and LAMP showed the same sensitivity, detecting leptospiral DNA in 12 out of the 48 MAT- positive sera. No detection was attained by either method in MAT-negative samples. These results show that it is possible to use LAMP for the detection of leptospirosis in non-human mammals. It also shows that, in the case of serum samples, MAT has higher diagnostic sensitivity than the currently available PCR and LAMP tests.