Exposure to ticks and seroprevalence of Borrelia burgdorferi among a healthy young population living in the area of southern Podlasie, Poland

Objectives. The objective of the study was assessment of risk of infection with Borrelia burgdorferi in the area of southern Podlasie in Poland, near the border with Belarus, by analysis of post-exposure procedure, and evaluation of asymptomatic infection in adolescents bitten by a tick, confirmed by serologic tests. Material and methods. The study was conducted among 128 healthy individuals aged 16–20 who declared being bitten by a tick. The level of IgM and IgG class antibodies was determined using the immunoenzymatic test (Borrelia 14 kD + OspC IgM ELISA and Borrelia IgG + VlsE ELISA, DRG Diagnostics). Positive and doubtful results were confirmed using the Western blot method (EUROLINE-WB, EUROIMMUN). Results. In the study group, the largest number of respondents (59.4%) declared tick bite in the region of the lower extremities, most often in the knee pit. Among the methods for removing the tick the largest number of respondents indicated removing it with the use of tweezers, with a simple, swift steady movement (29.7%), and pulling it out with the fingers (22.7%). In the ELISA test, a positive or doubtful result in at least one class was observed in 25.0% of respondents (n=32/128): in IgM class – 23.4% (n=30/128), and in IgG class – 4.7% (n=6/128). After verification with the Western blot test, infection was confirmed in 5.5% of respondents (n=7/128): in IgM class – 1.6% (n=2/128), in IgG class – 3.9% (n=5/128). In IgM class antibodies, the Western blot test confirmed positive or doubtful results of the ELISA test in 6.7%, while in IgG class antibodies in 83.3%. Conclusion. Evaluation of the actual infection with Borrelia spp. using serologic tests is difficult due to a certain non-specificity of the ELISA test, especially in IgM class antibodies, and difficulties with performance of a wide scope of specific Western blot tests. The variety of methods of tick removal declared by adolescents suggests that a wider education of society concerning appropriate methods of removing the tick should become an especially important element of prophylactic actions in the area of borreliosis.