Lyme borreliosis in Lithuania

The first cases of Lyme borreliosis in Lithuania were diagnosed in 1987, since when the number of reported cases has varied between 50 and 300 per year. In 1988, 354 cases were found through active surveillance. During 1988-91, 3,820 Ixodes ricinus ticks were collected in Lithuania; 11% of adult and 1% of nymphal ticks were infected with borrelia as determined by dark-field microscopy. Infected ticks were found in 27/31 (87%) of the regions investigated. Two isolates of Borrelia were obtained by in vitro cultivation and were shown to be Borrelia burgdorferi according to their reactions with species-specific monoclonal antibodies. From a survey of 6,187 people we estimated that 2,811/100,000 of the Lithuanian population are bitten by ticks every year. The prevalence of antibodies to B. burgdorferi measured by indirect IFA in healthy people varied between 4% and 32%, depending upon occupation and exposure to ticks.