Lyme borreliosis (LB) is a multisystemic disease caused by a cork-screw like bacterium from the Borrelia burgdorferi sensu lato complex. This disease is widely spread all over the Northern Hemisphere. In Europe LB is transmitted mainly by Ixodes ricinus ticks, in Asia  by I. persulcatus, and in North America by I. scapularis and I. pacificus.

Borrelia burgdorferi sensu lato is a complex of at least 17 genomic species (genospecies). Three of them are considered unequivocally pathogenic, causing various disease forms of LB in humans: Borrelia burgdorferi sensu stricto, B. afzelii a B. garinii. Apart from that B. lusitaniae, B. valaisiana and B. spielmanii were detested in biopsies of patients with LB symptoms, direct relationship with the disease was not proven, so far. Recently the evidence of potential pathogenic features of B. bissettii are appearing.

The disease itself may have various forms with various levels of severity, from asymptomatic cases, over localised or systemic skin infections, joint inflammations, to severe damages of central nervous system or heart. Antibiotic treatment is usually very successful, although in some cases the symptoms persist and do not respond to protracted antibiotic treatment. Different genospecies of B. burgdorferi sensu lato are associated with different clinical forms of LB. Apart from that the borelial genospecies differ also in geographical distribution and ecological features, like host preference etc.