DISPARITY OF BORRELIA-BURGDORFERI INFECTION-RATES OF ADULT IXODES-DAMMINI ON DEER AND VEGETATION

Rates of infection with Borrelia burgdorferi were compared in adult Ix odes dammini ticks collected from deer at one coastal and two island s ites with those collected from vegetation at the same sites. Ticks wer e examined using polyclonal direct fluorescent antibody. Spirochetes w ere observed in 47% of 288 ticks from vegetation as opposed to 13% of 276 ticks from deer (chi2, P < .001). This disparity was increased whe n only male ticks were compared. Among female ticks from deer, the inf ection rate was higher in flat than in engorged ticks. These findings may reflect spirochete loss from ingestion of borreliacidal antibodies in deer blood or may result from factors related to the sensitivity o f direct fluorescent antibody methods. They indicate that erroneously low estimates of regional risk for Lyme disease may be obtained if tic ks removed from deer are included in the determination of tick infecti on rates.