Distribution and prevalence of <i>Borrelia burgdorferi</i> sensu lato in <i>Ixodes ricinus</i> ticks of canton Ticino (Switzerland)

Free-living <i>Ixodes ricinus</i> ticks were collected from 12 different sites of canton Ticino, south of the Alps (Switzerland). Each tick was examined for the presence of <i>Borrelia burgdorferi</i> sensu lato (sl), the etiologic agent of Lyme borreliosis using direct fluorescent antibody assay, and isolation of the bacteria. <i>Borreliae</i> were characterized by PCR followed by RFLP. The abundance and infection rates of <i>I. ricinus</i> ticks varied greatly between the areas. Two localities were found free of <i>Borrelia</i>. The prevalence of infected ticks ranged from 5 to 19%. Most ticks (96%) were found infected by <50 spirochetes. Three <i>B. burgdorferi</i> sl species were successfully isolated: <i>B. garinii</i> dominated, followed by <i>B. lusitaniae</i> and <i>B. valaisiana</i>. Additionally, a mixed infection with <i>B. garinii</i> and <i>B. valaisiana</i> was observed. The distribution of the various <i>Borrelia species</i> in the different areas was heterogeneous. This is the first report of the presence of <i>B. lusitaniae</i> in <i>I. ricinus</i> in Switzerland.