Abstract

One hundred and ninety free-ranging rat individuals from dozens of sampling areas (towns, farms, villages) were investigated for Leptospira infections. From the renal tissues (kidneys and urinary bladders), DNA was extracted, and the samples were screened by an lfb1-specific PCR assay. The PCR products were sequenced. One hundred and three (54.2%) of the samples proved to be positive. All detected Leptospires belonged to the pathogenic phylogenetic cluster, and only one species was detected: all 103 positive samples belonged to L. interrogans lfb1 species group 1. In parallel, 353 human samples (urine, anticoagulated blood, tissues) from 232 patients over the period 2022–2025 submitted with suspected Leptospira infections were tested by commercial multiplex real-time PCR kits. Twenty-nine (8%) positive samples were found, which were retested by lfb1-specific PCR. The quality of 20 PCR products was sufficient for sequencing, representing 14 individual patients. Among the 14 positive patients we identified two Leptospira species: L. kirschneri lfb1 species group 6 in one case and L. interrogans in 13 cases (one lfb1 species group 3 imported case, 12 lfb1 species group 2). Comparison of the lfb1 sequences obtained from rats (lfb1: 1) and human cases (lfb1: 2, 1: 3, 1: 6) indicated that, although rat populations maintain the pathogen in high prevalence, they could not be the sources of the identified human Leptospira infections.

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