The impact of floods on the Leptospirosis outbreak in the Irkutsk Region

Background . In 2019, because of the past large-scale flood in the Irkutsk region, the infrastructure of eight municipal districts was destroyed. In the affected territory - Nizhneudinsky district, observations were made on the natural focus of leptospirosis. The aim . To assess the impact of the flood on the natural focus of leptospirosis. Materials and methods . Small mammals (SM) were counted and captured in flood-plain-marsh and forest-shrub stations. In 2012, 2014, 2019, 2021-2023, 493 SM individuals were captured. Biological material from humans and animals was examined using molecular biological and serological methods. Results . During the flood, the activity of the focus was significantly reduced, and in 2021-2022, an increase in the number (up to 22.0 % of hits per 100 l/s) and infection rate (up to 14.0 ± 5.3 %) of carriers in the focus was detected. In addition, agricultural and domestic animals can become a source of infection; for example, up to 90.0 ± 6.7 % of unvaccinated livestock have antibodies to leptospires. The high seroprevalence of the population (up to 20.0 ± 5.7 %) indicates sporadic contacts with the infection. Conclusion . The flood of 2019 contributed to a temporary decrease in the activity of the natural focus of leptospirosis, but later, there was a tendency for the epizootic situation to worsen. Therefore, preventive measures are necessary.