Detecting and predicting risks relayed to spread of natural foci infections on flood-affected territories in Irkutsk region

In summer 2019 in western Irkutsk region abundant and long rainfall caused a catastrophic flood that became a federal emergency. It resulted in a threat that natural infection foci would be activated in that emergency zone; given that, the Irkutsk Anti-plague Institute, together with Rospotrebnadzor territorial offices and regional veterinary authorities, conducted an epizootologic-epidemiologic study on affected territories in order to detect and predict possible epidemiologic risks. Totally, the study covered 30 socially significant objects and natural biotopes in three municipal districts in the region. We tested blood serum of people (244 samples), farm and home animals (253), and organs taken from caught small mammals aiming at determining natural foci infections in them with bacteriologic, serologic, and PCR procedures; overall. 4,370 examinations were performed. Share of immune people amounted to 13.1 % regarding tularemia; 17.5 %, tick-borne encephalitis; yersiniosis, 10.8 %; leptospirosis, 3.1 %; tick-borne borreliosis, 7.1 %. Antibodies to pathogenic leptospira were detected in 36.0-81.3 % farm animals and it can indicate there is a latent epizootic process. In July 2019 there was low population of synanthropic rodents in socially significant objects on affected territories and small mammals population also decreased in natural foci with high contagion rate for tularemia agent (down to 17.9 %). In September 2019 rats were detected to inhabit food-related objects and small mammals migrated actively in natural stations, contagion rate with tularemia agent going down among them whereas there was a growth in contagion rate with leptospira (up to 40.0%). We also revealed new natural tularemia and leptospirosis foci. Activity in natural infections foci didn’t exceed long-term average level just after the flood; still, there are persisting risks on affected territories in Irkutsk region that an epidemiologic situation might get worse there. The paper contains recommendations on further epizootologic-epidemiologic monitoring and organizing prevention activities such as control over sanitary situation at socially significant objects, local deratization, and sanitation in natural foci of animal leptospirosis.