PREVALENCE OF BORRELIA-BURGDORFERI SENSU LATE-INFECTED TICKS ON MIGRATING BIRDS

The prevalence of Lyme disease Borrelia-infected ticks on migrating bi rds was studied in Scandinavia. A total of 22,998 birds were caught at eight different bird observatories and examined for ticks, Five diffe rent species of ticks were found infesting the birds. The dominant spe cies, Ixodes ricinus, constituted 98.3% of the ticks collected. The pr esence of spirochetes was determined by an immunofluorescence assay of tick larvae and DNA amplification by PCR on all ticks, To determine w hich Borrelia burgdorferi sensu late species were present, a species c lassification was performed by DNA amplification with species-specific 16S rDNA primers and by DNA sequencing (rDNA is DNA coding for rRNA), Flagellin gene sequences of all species of B. burgdorferi sensu late previously recorded in Europe were observed. Borrelia garinii was the most prevalent Lyme disease Borrelia Species in ticks collected from b irds arriving from the South or Southeast in the spring, whereas the d istribution was more heterogeneous in ticks from birds migrating from the Southwest. These data support the notion that birds are partly res ponsible for the heterogeneous distribution of Lyme disease Borrelia s pirochetes in Europe.