Leptospirosis is a global zoonotic disease. Pathogenic Leptospira species colonize renal tubules, with some individuals becoming chronically infected. These maintenance hosts shed organisms in the urine to the environment, where they infect other hosts. Newly infected hosts may develop fever, jaundice, renal failure, and pulmonary hemorrhage or have no signs at all. This article addresses how Leptospira species evade the immune response and colonize renal tubules during chronic disease. Some of this is attributed to the differences in host susceptibility; other factors are involved, but many are speculative. During acute leptospirosis, kidney injury happens 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 renal immune response during chronic infection. Leptospires present in tubules may have a different antigenic profile, which facilitates evasion of an immune response. Development of therapeutic and control strategies could be improved with more knowledge about the chronic disease process; research continues on this front.

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 risk among pets. Varied clinical presentations and confusing diagnostic testing also make this condition 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, John JC, Nally JE. VET PATHOL 2009; doi:10.1354/vp.08-VP-0265-N-REV.