Risk factors associated with antibodies to leptospires in inner-city residents of Baltimore: a protective role for cats.

Leptospiral antibody prevalence was 16% in residents of Baltimore. Seropositivity was associated with age, gender, race, and bird ownership, reduced the antibody risk associated with age and race from odds ratios (95% confidence interval) of 3.3 (2.0, 5.5) and 3.3 (1.1, 9.3), respectively, to the baseline level. These data establish the high prevalence of leptospiral antibody in Baltimore and suggest a protective role for cats in reducing the risk of human infection.