Medical Entomologist US CDC Fort Collins, Colorado
Prevention and diagnosis of tick-borne diseases rely on an accurate understanding by the public and healthcare providers of when and where persons may be exposed to infected ticks. While tracking changes in the distribution of ticks and tick-borne pathogens provides fundamental information on risk for tick-borne diseases, metrics that incorporate prevalence of infection in ticks better characterize acarological risk. However, assessments of infection prevalence are more labor intensive and costly than simple measurements of tick or pathogen presence. Our objective was to examine whether data derived from repeated sampling at longitudinal sites substantially influences public health recommendations for Lyme disease prevention, or if more constrained sampling is sufficient. Here, we summarize inter-annual variability in prevalence of the agent of Lyme disease (Borrelia burgdorferi s.s.) in host-seeking I. scapularis nymphs and adults at 28 longitudinal sampling sites in the upper midwestern U.S. Infection prevalence was highly variable among sites and among years within sites. We conclude that monitoring infection prevalence in ticks aids in describing coarse acarological risk trends, but setting a fixed prevalence threshold for prevention or diagnostic decisions is not feasible given the observed variability and lack of temporal trends. Reducing repeated sampling of the same sites had minimal impact on regional (Upper Midwest) estimates of average infection prevalence; this information should be useful in allocating scarce public health resources for tick and tick-borne pathogen surveillance, prevention, and control activities.
