RISK OF INFECTION WITH BORRELIA-BURGDORFERI SENSU LATE FOR A HOST IN RELATION TO THE DURATION OF NYMPHAL IXODES-RICINUS FEEDING AND THE METHOD OF TICK REMOVAL

The objectives of the present study were to investigate the risk of B. burgdorferi s. l. (Bb)-transmission by I. ricinus-nymphs to a host (i ) after different periods of feeding, and (ii) with regard to the part icular method of tick removal. On each of 72 Mongolian gerbils 3 tick nymphs taken from a highly infected batch were allowed to feed in a sm all capsule. Feeding ticks were removed 16.7, 28.9, 47.0, and 65.2 hrs post-attachment. In each of these 4 groups 3 sub-groups with 6 gerbil s each were deticked by (a) pulling ticks out with forceps without any pretreatment, (b) pulling ticks out after 3 min of intensive squeezin g, and (c) applying nail polish to ticks 1.1 hrs before removal. The i nfection status in each gerbil was subsequently determined by larval x enodiagnosis. All gerbils with ticks removed greater than or equal to 47 hrs post-attachment were found to be infected. After 16.7 hrs as we ll as after 28.9 hrs of tick feeding, approximately 50% of the gerbils had acquired a transmissible infection, thus Bb-transmission to a hos t may even occur in the early phases of I. ricinus feeding. There is n o evidence from this study that the tick removal method used has any s ignificant influence on a host's Bb-infection risk.