We additionally report the seropositivity results based on ELISA only. combining enzyme-linked immunosorbent assay tests and line immunoblots. We calculated the PVR odds of being classified as IgG or IgM positive as a function of age, sex, Eltrombopag Olamine and educational level using binomial logistic regression models. We applied varying seropositivity classifications and weights considering age, sex and education to compensate for differences between the sample and regional population characteristics. Results IgG antibodies for Eltrombopag Olamine s.l. were present in 2.4% and IgM antibodies in 0.6% of the participants (weighted: 2.2% [IgG], 0.6% [IgM]). The likelihood of IgG seropositivity increased by 3.0% (95% confidence interval [CI] 1.5C5.2%) per 1?year increase in age. Men had 1.65 times the odds for IgG seropositivity as women (95% CI 1.01C2.73), and highly educated participants had 1.83 times the odds (95% CI 1.10C3.14) as participants with an intermediate level of education. We found no statistically significant link between age, sex, or education and IgM seropositivity. Our weighted and age-standardized IgG seroprevalence was comparable to the preceding serosurvey German Health Interview and Examination Survey for Adults (DEGS) for NRW. Conclusions We confirmed that increasing age and male sex are associated with increased odds for IgG seropositivity and provide evidence for increased seropositivity in the highly educated group. s.l.?seropositivity remained constant over the past decade in this regional German population. Graphical abstract Keywords: Lyme disease, Seroepidemiological studies, Immunoglobulin G, Immunoglobulin Eltrombopag Olamine M, Antibodies, Ticks, Enzyme-linked immunosorbent assay, Immunoblotting, Tick-borne diseases, Germany Background Lyme borreliosis is the most prevalent tick-borne disease in Europe [1]. From 2013 to 2017, yearly reported incidence for Lyme borreliosis in German states with disease notification ranged from 26 to 41 reported cases per 100,000 inhabitants [2]. However, incidence data from German health insurance?funds for 2019 indicate 429 diagnoses per 100,000 insured persons for Germany [3]. For North Rhine-Westphalia (NRW), the insurer Nordrhein reported 99 diagnoses per 100,000 insured persons and the insurer Westfalen-Lippe reported 135 diagnoses per 100,000 insured persons [3]. In addition, yearly incidence between certain regions varies enormously; for example, in 2017 and within Mecklenburg-Western Pomerania, over 160 cases per 100,000 persons were reported in the west, and less than 40 cases per 100,000 persons were reported in the east. Moreover, changes over time have also been observed recently; Lyme borreliosis incidence in Bavaria, for instance, increased from 23.2 per 100,000 inhabitants in 2015 to 47.4 per 100,000 inhabitants in 2020 [4]. In all, the picture is highly heterogeneous regarding information from different data sources, regions and time. Spirochaetes of the genospecies complex sensu lato (s.l.), the causal agent of Lyme borreliosis [5], are detectable in about 3C35% of ticks in Germany Eltrombopag Olamine [6C12]. Of at least 18 unique known genospecies of s.l., and are the three major genospecies in Europe [13], transmitted to humans by ticks (complex occur in Europe mainly between March and October, peaking from June to August [2]. Since climate change is leading to higher mean temperatures [17, 18], tick season will potentially be prolonged [19] and could continue throughout the winter in Germany if temperatures are mild [20]. An increase in annual air temperature by 1?C was observed for NRW (1961C1990 compared to 1991C2020) [21]. At the same time, the number of days with ice and frost decreased. The warmer winters with less snow may promote an earlier food Eltrombopag Olamine supply for wild boars and other potential hosts for ticks (genospecies distributions and anthropogenic factors (e.g. recreational activities) [23], it is difficult to predict whether or to what extent climate change will change the infection risk with s.l. [19, 24, 25]. Tick density was found to increase in a nature reserve, Siebengebirge, near Bonn, from 1987/1989 until 2008 [26]. Also, rising tick infection proportions have been reported for this area, where the number of ticks carrying spirochaetes increased 2.5-fold within a decade [27]. However, the genospecies distribution also changed over this time period. In 2001, and were the dominant species in the Siebengebirge. Thus, the distribution of genospecies has to be taken into account when looking at changes in tick infection proportions. Further, there were considerable differences in genospecies distributions among the three different tick collection sites.