Leptospirosis is a global zoonotic disease. Pathogenic Leptospira colonize renal tubules, and some individuals become chronically infected. These maintenance hosts shed organisms in the urine to the environment. Newly infected hosts may have no clinical signs or may develop signs, such as fever, jaundice, renal failure, and pulmonary hemorrhage. This review addresses how Leptospira organisms evade the immune response to colonize renal tubules during chronic infection. Part of the explanation is differences in host susceptibility.Other factors are involved, but many are speculative.During acute leptospirosis, kidney injury occurs early; in animals with chronic disease, however, kidney damage may develop weeks or months after infection. Little is known about what factors influence disease progression and the host’s renal immune response during chronic infection. Leptospires present in tubules may have a different antigenic profile,which facilitates evasion of an immune response.Research continues to discern how Leptospira evades the immune system. Further knowledge about the chronic disease process might aid in the development of therapeutic and control strategies.

COMMENTARY: Leptospirosis among pet dogs in the United States continues to be an underdiagnosed disease.Wildlife reservoirs such as raccoons are increasing in urban and suburban areas, increasing the risk among pets.Varied clinical presentations and confusing diagnostic testing also make it a challenge to the clinician.Vaccination is available for several serovars,making it a preventable disease in many cases.—Patricia Thomblison, DVM,MS

Host-pathogen interactions in the kidney during chronic leptospirosis. Monahan AM, Callanan JC,Nally JE.VET PATHOL doi:10.1354/vp.08-VP-0265-N-REV