Tick-borne borreliosis in the archipelago of southern Sweden.

Sera from 480 individuals living on an island at the Baltic coast in southern Sweden were tested by ELISA for detection of antibodies against Borrelia burgdorferi. The area was found to be highly endemic for Lyme borreliosis with elevated IgG antibody levels in 90/480 individuals (19%). Of 149 ticks collected on the island 16 nymphs (17%) and 15 adults (26%) were infected by B. burgdorferi. The occurrence of antibodies to B. burgdorferi increased with age and time spent in the endemic area. Infection without manifest disease seemed to dominate since only 18/480 (4%), or 6/90 (7%) with positive serology, had been treated for Lyme borreliosis. However, the prevalence of symptoms associated with late manifestations of Lyme borreliosis e.g. arthralgia, chronic skin efflorescences or neurologic disorders was significantly higher among seropositive compared to seronegative individuals.