A Northern vs. Southern United States Comparison of Host Infestation by the Lyme Borreliosis Vector, Ixodes scapularis

The prevalence of human and canine Lyme disease varies on a latitudinal cline in central and eastern United States, with much higher prevalence in the northern U.S. However, the Lyme disease vector, Ixodes scapularis , and reservoir hosts for the Lyme etiological agent Borrelia burgdorferi occur sympatrically throughout the southern U.S., so it is unclear why disease prevalence varies in this way. I captured Borrelia reservoir hosts at the Savannah River Site (SRS), Aiken, South Carolina and at the Pinelands Field Station (PFS), New Lisbon, New Jersey to further elucidate the role that hosts play in Lyme disease patterns in these two representative locations in the eastern U.S. that differed dramatically in human Lyme disease prevalence. I compared patterns of host utilization by larval and nymphal I. scapularis and collected questing ticks from the environment to measure host species composition, intensities on key hosts (particularly Peromyscus spp. and Plestiodon spp.), and patterns of tick attachment sites on hosts in order to better understand the Borrelia sylvatic cycles in the north and southeastern U.S. I found well-defined nymphal and larval activity peaks with emergence of questing and on-host I. scapularis nymphs preceding that of larvae. Both juvenile life stages were active earlier in the spring and summer seasons at SRS than at PFS. At SRS 81% of the 261 immature I. scapularis collected from hosts came from lizards, while only 1.0% of 496 immature I. scapularis came from lizards at PFS. At SRS the most commonly parasitized host overall was the lizard Plestiodon laticeps, with 60% of host individuals parasitized and a mean intensities of 3.07 (+/- 20 0.94SE) immature I. scapularis on these parasitized individuals. In comparison, at PFS the mouse Peromyscus leucopus was the most commonly parasitized host overall (51% hosted ticks) and had the highest mean intensities of the parasitized species (6.86 +/- 1.77SE). I also found significant differences in attachment locations of immature I. scapularis on Sorex and Peromyscus between the two study sites. These differences in I. scapularis host utilization, my very low success sampling questing juvenile I. scapularis from vegetation, and the high occurrence of ticks on lizards indicate that there are important differences in I. scapularis behavior in the southeastern compared to the northeastern U.S. It appears that southern juvenile I. scapularis target lizard hosts by questing within the leaf litter, rather than above the leaf litter as in the northeast. If so, then human encounters with these ticks could be less frequent; this suggests promising future research directions.