Leptospira interrogans in Norway rats from Barcelona, Spain

Background Leptospirosis is an under-diagnosed zoonotic emerging disease caused by pathogenic Leptospira and is primarily maintained in the environment by rodents, which serve as its main reservoir in urban settings. Information of Leptospira prevalence in urban rats in Spain is scarce. We aimed to investigate the presence and prevalence of pathogenic Leptospira in rats of the sewer system and parks of Barcelona at two different time-points. Methods Rattus norvegicus were captured over two different sampling periods in ten different Barcelona districts. Kidney and bladder samples were tested to detect pathogenic Leptospira by real-time PCR and sequenced to determine Leptospira species. Results A total of 82 rats were sampled in 2017 whereas 136 rats were sampled in 2021-2022. In the first sampling period we found 12% of rats were positive for L. interrogans whereas in the second sampling period L . interrogans was found in 4% of the tested rats. L. interrogans infected rats were present in seven Barcelona districts. In our study, L. interrogans was detected in both kidney and bladder tissues. Conclusions Our results demonstrate the presence of L. interrogans in urban rats, supporting the need to promote One Health surveillance programs to detect pathogenic Leptospira in Barcelona.