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.

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