Regional and demographic patterns of seroprevalence of Borrelia burgdorferi IgG and IgM antibodies in blood donors in Austria.

Knowledge about the epidemiology of Lyme borreliosis in Austria remains limited. We conducted a nationwide cross-sectional study among blood donors from all Austrian provinces to assess the exposure to Borrelia burgorferi sensu lato. A total of 1841 serum samples from blood donors aged between 18 and 69 years were tested for Borrelia-specific IgG and IgM. Associations with age, sex, province and the residential altitude were assessed for both the one-tier and two-tier methods. IgG seroprevalence was 14% for one-tier and 7% for the two-tier. A consistent increase in age was observed for both approaches. Using the 20-29-year age group as reference, the strongest association was observed in individuals aged 60-69 years. The IgG positivity was higher among males than females for both the one-tier and two-tier tests. Regional analysis revealed substantial variation in IgG seroprevalence, with the lowest prevalence recorded in Tyrol and the highest in Carinthia. These differences were not attributable to age distribution. An additional analysis revealed a correlation between the seroprevalence and the altitude of residence. IgM seroprevalence did not differ significantly between the one-tier and two-tier approaches (7% and 6%), and no age-, sex-, or region-related trends were identified. Our findings demonstrate demographic and regional differences in exposure to Borrelia burgdorferi. Higher altitude of residence is associated with reduced exposure to the spirochetes. The findings emphasize the importance of Lyme borreliosis surveillance and help identify the groups and areas most likely to profit from targeted prevention.