Advances in investigations of Lyme borreliosis in the territory of the former USSR.

Whereas late manifestations of Lyme borreliosis were described in Russia more than 100 years ago, early manifestations were described as different disease entities such as tick-borne erythema, etc. In 1985 Lyme borreliosis was first verified serologically and the agent was first identified in 1986. By the beginning of 1992 Lyme borreliosis was serologically confirmed in patients from the Baltics to the Far East. Their geographical patterns in Russia are closely related to areas of the hard ticks Ixodes persulcatus and Ixodes ricinus which are also the main vectors of tick-borne encephalitis virus. As in the case of this infection, in the west of Russia there are "ricinus" natural foci of Lyme borreliosis, and to the east there are similar "persulcatus" foci; through large territories in the East Europe there are common foci for both species. Many Borrelia burgdorferi strains of tick origin have been isolated from various regions of Russia and neighbouring republics. Adult tick infection rates vary from several per cent to 30% in I. ricinus and up to 50-60% in I. persulcatus. Double infections of Lyme borreliosis spirochetes and tick-borne encephalitis virus have been recorded for ticks as well as for humans. Lyme borreliosis morbidity and its importance for the Russia territory are discussed.