Sarah Canterberry, Daniel Bennett, Robert J. Wiggers
Background: Bacteria within the genus Rickettsia are obligate intracellular parasites, spread by arthropod vectors, that cause a number of human illnesses. In the United States, Spotted Fever Rickettsioses have been increasing for the past 4 years, and an increasing number of pathogenic or suspected pathogenic species of Rickettsia are being found in ticks. Multiple studies have indicated that up to 70% of ticks may carry one or more species of Rickettsia and have the potential to spread them to humans. The purpose of this study was to determine the extent to which ticks carried Rickettsia sp. bacteria in the eastern Texas area.
Methods and Findings: 35 ticks, 29 Ixodes sp. and 6 Amblyomma maculatum, were collected and subjected to total DNA isolation. PCR amplifications were performed using primers for the 17 kDa antigen for Rickettsia sp. in all ticks. 20 of the Ixodes ticks and 1 A. maculatum were positive for Rickettsia. The positive A. maculatum DNA was then subjected to PCR amplification using primers specific for R. parkeri, the causal organism of Tidewater fever for which A. maculatum is the only known vector. Overall, 21 of the 35 ticks (60%) were demonstrated to be carrying Rickettsia sp. bacteria; PCR confirmed that the single positive A. maculatum tick was carrying R. parkeri.
Conclusions: In the eastern Texas area, a significant proportion of ticks carry potential rickettsia pathogens. Physicians should consider the possibility of a rickettsial infection when a patient presents with a febrile illness and reports exposure to ticks.
