PHYSICIAN-DIAGNOSED ERYTHEMA MIGRANS AND ERYTHEMA MIGRANS-LIKE RASHESFOLLOWING LONE STAR TICK BITES

Objective: To differentiate cases of physician-diagnosed erythema migr ans and erythema migrans-like rashes associated with Lone Star tick (A mblyomma americanum) bites. Design: Retrospective case series. Setting : Private primary care clinic in rural Missouri. Patients: Seventeen p atients with physician-diagnosed erythema migrans following a definite Lone Star tick bite at the rash site. Interventions: A biopsy was per formed on all rash sites. All patients were treated with oral antibiot ics. Main Outcome Measures: Rash appearance, size, body location, mult iple lesions, incubation time, associated symptoms, seasonal occurrenc e, histopathological features, tick stage and sex, patient age and sex , treatment response, growth in BSK II culture media, and serologic ev aluation. Results: Rashes associated with Lone Star ticks were similar to erythema migrans vectored by other Ixodes ticks. Differences were noted in Lyme disease serology results, especially flagellin-based enz yme immunoassays, and failure to yield spirochetes in BSK II cultures. Lyme serology results were often negative, but were also frequently i nconsistent viith results of controls without Lyme disease. Conclusion s: Lone Star ticks are associated with rashes that are similar, if not identical, to erythema migrans associated with borrelial infection. T he recent isolation and cultivation of Borrelia burgdorferi from ticks (including 1 Lone Star tick) from the farm of a patient included in t his report has raised the possibility that Lone Star ticks are ''bridg e vectors'' for human borrelial infection. Although further investigat ion is needed, these rashes may be secondary to spirochetal infection.