A prospective study on the incidence of Borrelia burgdorferisensu lato infection after a tick bite in Sweden and on the Åland Islands, Finland (2008–2009)

Lyme borreliosis (LB) is a common and increasing tick-borne disease in Europe. The risk of acquiring a Borreliainfection after a tick bite is not fully known. Therefore, we investigated the incidence of Borreliainfection after a bite by a Borrelia-infected tick and if the Borreliaload and/or the duration of tick-feeding influenced the risk of infection. During 2008–2009, ticks and blood samples were collected from 1546 tick-bitten persons from Sweden and the Åland Islands, Finland. Follow-up blood samples were taken 3 months after the tick bite. The duration of tick feeding was microscopically estimated and Borreliawas detected and quantified in ticks by real-time PCR. Anti-Borreliaantibodies were detected in sera using ELISA tests and immunoblot.