A retrospective study of 9,335 cases of human leptospirosis in the state of São Paulo, Brazil, diagnosed between 1969 and 1997 showed that the disease is endemic throughout the state. Middle-aged adults, with a range of 20-39 years, were most frequently infected (32.40%). The mean annual incidence was 0.53 per 100,000 population and the disease was more frequent in males (87.0%). Cases occurred mainly in January to April each year. A peak was observed in 1991 and 1996 which rainfall average was 159.9 and 160.3, respectively. These data emphasize the potential public health importance of leptospirosis in the state of São Paulo, Brazil.

A polymerase chain reaction (PCR)-based assay which amplifies repetitive DNA elements present within bacterial genomes was used to characterize and differentiate Leptospira sp. Thirty-five strains from a reference culture collection and 18 clinical isolates which had been previously analyzed by cross agglutinin absorption test (CAAT) were evaluated by this technique. PCR results from analysis of the reference culture collection showed no bands corresponding to serogroups Australis, Autumnalis, Bataviae, Celledoni, Cynopteri, Djasiman, Panama, Pomona, Pyrogenes, and Tarassovi. However, the PCR method was able to clearly discriminate the serogroups Andamana, Ballum, Canicola, Grippotyphosa, Hebdomadis, Icterohaemorrhagiae, Javanica, Sejroe, Semaranga, and Shermani. Clinical isolates previously characterized by CAAT as serovar Copenhageni, serovar Castellonis, and as serovar Canicola were in agreement with PCR results. The clinical isolate previously characterized as serovar Pomona was not differentiated by PCR. Forty additional clinical isolates from patients with leptospirosis obtained in São Paulo, Brazil were also evaluated by this PCR method. Thirty-nine of these were determined to belong to serogroup Icterohaemorrhagiae (97.5%) and one to serogroup Sejroe (2.5%). These results demonstrate that the PCR method described in this study has utility for rapid typing of Leptospira sp. at the serogroup level and can be used in epidemiological survey

The zoonotic disease leptospirosis is caused by pathogenic species of the genus Leptospira and was recently included in the list of Neglected Diseases by the World Health Organization. Leptospirosis burden is estimated to have over a million human cases and cause 60 thousand deaths annually, in addition to its economic impact and veterinary concern. The microscopic agglutination test (MAT), recommended by the World Health Organization, exhibits reduced sensitivity at the beginning of the disease, in addition to being technically difficult. New recombinant antigens are being pursued for rapid and specific serodiagnostic tests, especially in the initial phase of the disease, and chimeric multiepitope proteins are a strategy with a great potential to be implemented in serology. Based on previous subproteomic results, we designed a synthetic construct comprising 10 conserved leptospiral surface antigens, and the recombinant protein was purified and evaluated regarding its diagnostic potential. The protein termed rChi2 was recognized by antibodies in serum from patients both at the onset (MAT−) and in the convalescent (MAT+) phase in 75 and 82% of responders, respectively. In addition, rChi2 immunization in hamsters elicited a strong humoral response, and anti-rChi2 antibodies recognized several immobilized intact Leptospira species, validating its potential as an early, broad, and cross-reactive diagnostic test.