The same strain leading to different clinical outcomes: The enigma behind the canine leptospirosis

Canine leptospirosis is a worldwide zoonosis, varying from asymptomatic and chronic infections to clinical acute disease. In many parts of the world Leptospira interrogans serogroup Icterohaemorrhagiae strains have great epidemiological importance, being the most prevalent on dogs. The present study aims to characterize and compare strains/sequences belonging to the serogroup Icterohaemorrhagiae recovered from clinically ill and asymptomatic dogs. Based on secY gene sequences of L. interrogans serovar Icterohaemorrhagiae, we have studied genetic diversity of strains obtained from 13 dogs, including dogs with clinical signs of acute leptospirosis, asymptomatic dogs and animals with chronic kidney disease, all of them from the same geographical area, the state of Rio de Janeiro, Brazil. No genetic variations on secY gene were observed between strains/groups. No significant associations were observed between clinical status and age, sex or vaccinal status. The same strain leads to different clinical outcomes on canine leptospirosis. The answer for this will rise from deep studies regarding whole genomic sequencing of the strains, as well as proteomics. Those studies may provide key information for understanding of the clinical manifestation of the disease.