Occurrence and prevalence of host-seeking Ixodes ricinus nymphs infected with Borrelia burgdorferi (sensu lato) genospecies in Europe (1999–2022)

Ticks of the Ixodes ricinus complex are the primary vectors of Borrelia burgdorferi (sensu lato), the complex of genospecies that cause Lyme borreliosis, in Europe and North America. We summarized the tick surveillance data of host-seeking I. ricinus nymphs in Europe between 1999 and 2022 to quantify and map the occurrence and B. burgdorferi (s.l.) genospecies infection prevalence (NIP) across the continent in high resolution. Geocoordinates or reported subnational administrative units were extracted where tick surveillance data were collected and validated with previous systematic literature reviews to ensure comprehensiveness. Data were grouped according to country, year, and individual B. burgdorferi (s.l.) genospecies and quantified via random effects. In total, 278,189 host-seeking nymphs from 152 studies across 27 European countries were extracted. Overall NIP was 11.1% across Europe, with the highest NIP in eastern European countries (> 27%) and the lowest NIP within the United Kingdom (< 4.2%). Borrelia afzelii had the broadest distribution and highest NIP among the genospecies (4.7%). Importantly, this work provides a publicly available and highly precise geographically comprehensive database of the relative abundance and prevalence of B. burgdorferi (s.l.) infection in host-seeking I. ricinus nymphs in Europe. These data can be utilized by researchers for further use and analyses of Lyme borreliosis.