Rickettsia parkeriin Gulf Coast Ticks, Southeastern Virginia, USA

We report evidence that Amblyomma maculatum tick populations are well established in southeastern Virginia. We found that 43.1% of the adult Gulf Coast ticks collected in the summer of 2010 carried Rickettsia parkeri, suggesting that persons living in or visiting southeastern Virginia are at risk for infection with this pathogen. R ickettsia parkeri is an obligate intracellular bacterium belonging to the spotted fever group of rickettsiae; this organism has recently been found to be pathogenic to humans (1). Infection with R. parkeri can be considered an emerging infectious disease, referred to as R. parkeri rickettsiosis, American Boutonneuse fever, and Tidewater spotted fever. Two confi rmed cases of R. parkeri infections, including the index case in 2002, occurred in southeastern Virginia (1-3). Since then, 20 R. parkeri infections have been reported, mainly from the southern United States (2). In the United States, Amblyomma maculatum (family Ixodidae) ticks, commonly referred to as Gulf Coast ticks, are the only known natural vector of R. parkeri. A. maculatum ticks have been reported from 12 states: Alabama, Arkansas, Florida, Georgia, Kansas, Kentucky, Mississippi, Oklahoma, South Carolina, Tennessee, Texas (1,4,5), and Virginia (6). Sonenshine et al. reported fi nding individual A. maculatum ticks in Virginia in 1965 but concluded that populations had not become established (7).