Tick bites, clinical symptoms of Lyme borreliosis, and Borrelia antibody responses in Finnish army recruits training in an endemic region during summer.

Tick bites, associated clinical symptoms, and antibodies against Borrelia burgdorferi were investigated in 77 Finnish army recruits training during summer in an endemic region and 50 control recruits serving outside the habitat of ticks. During a follow-up of 6 months, 26.9% of the study recruits reported tick bites. None gave a history of erythema migrans. Five study recruits and none in the control group had a combination of two or three nonspecific symptoms compatible with Lyme borreliosis. Three of these five study recruits had been bitten by several ticks. Thirteen (16.9%) study recruits and two (4.0%) control recruits had positive antibody levels against B. burgdorferi in their first serum specimens. No significant change in immunoglobulin G antibody levels was seen between the first and second specimens. Immunoglobulin M antibody levels increased in the sera of 13 (11.9%) study recruits and 1 (3.0%) control recruit. We conclude that recruits training in tick habitats are at high risk of tick bites. All recruits starting their military training in endemic areas should be taught to recognize and remove ticks and advised to wear protective clothing.