Human Infecting with Tick-Borne Diseases on the Territory of Irkutsk City: 25 Years of Survey

Abstract

Background. The existence of antropogenic foci of Ixodid tick-borne infections (TBI) have been registered on the territory of many cities during several last decades. The infected ticks’ biting occurs directly in urban conditions. There is a lot of publications devoted to ticks and their hosts studying in the urbanized landscapes, but much less data concerning human infecting after tick bite in these conditions.Аim – the comparative analysis of the cases of human infecting with TBI within the city limits and beyond, and determination the sites of infection risk on the territory of Irkutsk.Material and methods. The epidemiological investigation cases records from Irkutsk Regional Center for Hygiene and Epidemiological Surveillance have been analyzed: tick-borne encephalitis (TBE, n = 1607), ixodid tick-borne borrelioses (ITBB, n = 938) dated 1995–2019 and tick-borne rickettsiosis (TBR. n = 270) dated 2001–2019. Statistical analysis was computed in Microsoft Excel Software. The map of infecting sites is made in ArcGis Soft (ESRI, USA).Results. According to the patients reports, 281 of all registered TBI cases during period under the review, occurred within the city limits. There were 115 TBE cases (7.2% of all TBE cases registered among Irkutsk citizens), 139 ITBB (14.8%) and 27 TBR (10.0%). 86.5% of the patients associate their disease with tick bite. There are no valid linear trends in the dynamics of TBE and ITBB from 2001 (with available information on all three infections) up to the end of period under the review, but significant growth trend in TBR incidence. The groups of patients, infected within and beyond the city limits, differ in some ecological and demographical parameters and also in structure of TBI morbidity. Tree area groups with different risk level for TBI contracting have been determined in the city.Conclusion. Judging by the fact that TBI occurs annually on the territory of the city, it is likely that there are perennial anthropogenic foci within its boundaries, which must be identified and studied all of their components.