Lyme borreliosis is the most common vector-borne bacterial infection in the temperate northern hemisphere. In the United States of America over 35,000 confirmed or probable cases were reported by state health departments to the Centers for Disease Control and Prevention (CDC) in 2008. It is likely that well over 100,000 cases occur in Europe each year. Lyme borreliosis is caused by several genospecies of Borrelia burgdorferi sensu lato, which are transmitted by ticks of the Ixodes ricinus complex. The infection occurs most commonly in forested, woodland and heathland habitats that support the lifecycles of Ixodes ticks and the small mammals and birds that are reservoir-competent hosts for B burgorferi. The most common presenting feature of Lyme borreliosis is erythema migrans, a slowly spreading rash. The spirochaetes can disseminate through the bloodstream and lymphatics to other organs and tissues and cause later manifestations, most commonly affecting the nervous and musculoskeletal systems. The infection responds to appropriate antibiotic treatment at any stage of disease, with excellent outcomes in most cases, but patients with severe tissue damage from previously untreated late stage disease may recover incompletely. A small proportion of patients can have persistent non-specific symptoms following treatment, without evidence of continuing active infection. This has been termed “post-Lyme syndrome” and appears to be similar to other post-infection syndromes. Prevention relies mainly on personal protection measures against tick bites.
Geographical and genospecies distribution of Borrelia burgdorferi
sensu lato DNA detected in humans in the USA
