Holly Gaff

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  Epidemiology of tick-borne Rickettsia spp.
  Holly Gaff

  The incidence of tick-borne rickettsial disease in the southeastern United States has been rising steadily through the past decade, and the range expansions of tick species and tick-borne infectious agents, new and old, has resulted in an unprecedented mix of vectors and pathogens. The results of an ongoing 5-year surveillance project describe the relative abundance of questing tick populations in southeastern Virginia. Since 2009, more than 100,000 questing ticks of a variety of species have been collected from vegetation in a variety of habitats, with Amblyomma americanum constituting over 95% of ticks collected. We found that 26.9–54.9% of A. americanum ticks tested were positive for Rickettsia amblyommii, a non-pathogenic symbiont of this tick species. Rickettsia parkeri was found in 41.8–55.7% of Amblyomma maculatum ticks. The rate of R. parkeri in A. maculatum ticks is among the highest in the literature and has increased in the 2 years since R. parkeri and A. maculatum were first reported in southeastern Virginia. Additionally, R. parkeri is started to be found in A. americanum ticks throughout the region. While this is at extremely low prevalence, the sheer abundance of these ticks may increase the encounters with rickettsial agents with the potential for increased risk to human health.