Distribution of clinically relevant Borrelia genospecies in ticks assessed by a novel, single-run, real-time PCR

A LightCycler-based PCR protocol was developed which targets the ospA gene for the identification and quantification of the different Borrelia burgdorferi sensu lato species in culture and in ticks, based on the use of a fluorescently labeled probe (HybProbe) and an internally labeled primer. The detection limit of the PCR was 1 to 10 spirochetes. A melting temperature determined from the melting curve of the amplified product immediately after thermal cycling allowed the differentiation of the three different B. burgdorferi sensu lato genospecies (B. burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii) that are clinically relevant in Europe in a single PCR run. This method represents a simplified approach to study the association of different Borrelia species in ticks, the risk of Lyme borreliosis, and the putatively species-specific clinical sequelae. To determine the reliability of the real-time PCR protocol, we studied the prevalence of B. burgdorferi sensu lato infection in Ixodes ricinus ticks. A total of 1,055 ticks were collected by flagging vegetation in five different sites in the region of Konstanz (south Germany) and were examined for the distribution of B. burgdorferi species by real-time PCR. The mean infection rate was 35%. Of 548 adult ticks, 40% were positive, and of 507 nymphs, 30% were positive. The predominant genospecies (with 18% mixed infections) in the examined areas was B. afzelii (53%), followed by B. garinii (18%) and B. burgdorferi sensu stricto (11%); 0.8% of the infecting Borrelia could not be identified.