TRANSMISSION RISK OF LYME-DISEASE AND IMPLICATIONS FOR TICK MANAGEMENT

Transmission risk of Lyme disease at a site can be estimated using the probability of exposure (P1 = probability of being bitten by at least one infected tick); P1 = 1 -(1 - k(t))n, where n = number of tick bit es per person and k(t) = spirochete prevalence in questing ticks. This probability is more directly related to the likelihood of acquiring L yme disease than the standard measure of transmission risk (the number of infected ticks per sample) and allows for direct consideration of the level of tick/human contact (by varying n) in assessing exposure r isk and designing management strategies. Projections predict that inte rventions that lower tick abundance or spirochete prevalence do not ne cessarily result in equivalent declines in human exposure risk. Manage ment interventions are predicted to have greatest success at lowering disease incidence in humans when tick abundance and/or pathogen preval ence in questing ticks are initially low (e.g., for ticks in residenti al lawns or for low-prevalence diseases). These techniques are predict ed to be less effective at lowering disease incidence in people engage d in high-risk activities at sites with high tick abundance and pathog en prevalence, such as wooded sites in highly endemic areas.