The Study of Community Immunity to the Tick-Borne Encephalitis Virus in One of the Non-Endemic Areas of the Khabarovsk Krai (the Tuguro-Chumikansky District)

Abstract

Introduction. At present, the areas endemic for tick-borne encephalitis (TBE) tend to expand. Monitoring of TBEV antibody detection rates in the population of non-endemic areas in order to adopt timely measures for specific and non-specific disease prevention thus acquires particular importance. The Tuguro-Chumikansky District is not among the endemic areas of the Khabarovsk Krai. Yet, the rise in the number of people seeking medical attention for an ixodes tick bite and TBE rates in the local population has been registered recently. Our purpose was to establish the level of natural herd immunity to the tick-borne encephalitis virus in the population of the Tuguro-Chumikansky District. Materials and methods. We conducted a serological survey among unvaccinated permanent residents of 6 villages of the study district. Results. The highest TBEV antibody detection rates were registered in the examined residents of the villages of Tugur (61.3 ± 8.75%) and Udskoye (51.4 ± 8.22%). On the whole, specific immunoglobulins for the tick-borne encephalitis virus were found in 29.4 ± 2.26% of the subjects, thus indicating that the locals have contacts with infected vectors or have possibly suffered from the inapparent (subclinical) infection. Discussion. The established immunoglobulin G detection rates and immunity levels to TBEV may show that the population of the Tuguro-Chumikansky District is involved in the epidemic process. A further increase in the number of people bitten by ticks can lead to an increase in the registered TBE incidence in the district making it yet another regional area endemic for the disease.