Factors associated with clinical leptospirosis: a population-based case-control study in the Seychelles (Indian Ocean)

Background In Western countries, leptospirosis is uncommon and mainly occurs in farmers and individuals indulging in wafer-related activities. In tropical countries, leptospirosis can be up to 1000 times more frequent and risk factors for this often severe disease may differ. Methods We conducted a one-year population-based matched case-control study to investigate the frequency and associated factors of leptospirosis in the entire population of Seychelles. Results A total of 75 patients had definite acute leptospirosis based on microagglutination test (MAT) and polymerase chain reaction (PCR) assay (incidence: 101 per 100 000 per year; 95% confidence interval [CI] : 79-126). Among the controls, MAT was positive in 37% (past infection) and PCR assay in 9% (subclinical infection) of men aged 25-64 with manual occupation. Comparing cases and controls with negative MAT and PCR, leptospirosis was associated positively with walking barefoot around the home, washing in streams, gardening, activities in forests, alcohol consumption, rainfall, wet soil around the home, refuse around the home, rats visible around the home during day time, cats in the home, skin wounds and inversely with indoor occupation. The considered factors accounted for as much as 57% of the variance in predicting the disease. Conclusion These data indicate a high incidence of leptospirosis in Seychelles. This suggests that leptospires are likely to be ubiquitous and that effective leptospirosis control in tropical countries needs a multifactorial approach including major behaviour change by large segments of the general public.