Southern Tick-Associated Rash Illness -- When a Bull's-Eye Rash Isn't Lyme Disease

Lone Star Ticks

Both patients and providers have wondered whether the lone star tick spreads Lyme disease. Repeated studies have found no evidence to support this concern. On the contrary, studies have shown that saliva of the lone star tick is naturally toxic to the Lyme disease spirochete, Borrelia burgdorferi.

Although it's not always possible to differentiate between STARI and Lyme disease on the basis of geography, it is frequently possible to distinguish between lone star ticks and blacklegged ticks and thus narrow the differential diagnosis. Female lone star ticks are particularly distinctive, with noticeable white dots or "stars" on their backs (Figure 3), which some patients will remember.^[2]

Figure 3. Lone star ticks. Figure courtesy of CDC.

Summary

In southern and southeastern regions of the United States where Lyme disease is rare, patients who present with a bull's-eye rash and no travel history probably have STARI, a condition of unknown etiology that appears after the bite of a lone star tick. Given the difficulty of differentiating STARI from Lyme disease clinically, some healthcare providers choose to treat patients with suspected STARI with the same course of antibiotics that is used to treat Lyme disease. Whether antibiotic treatment is necessary is unknown.

When evaluating a patient for a known lone star tick bite, it is important to remember that lone star ticks are vectors for ehrlichiosis and tularemia, both potentially fatal illnesses. For more information on STARI, see www.cdc.gov/STARI. For more information on tick bites, please visit www.cdc.gov/ticks.

Web Resources

CDC Southern Tick-Associated Rash Illness

CDC: Ticks

Alison Hinckley, PhD, is an epidemiologist with the US Centers for Disease Control and Prevention, Division of Vector-Borne Diseases, in Fort Collins, Colorado. Dr. Hinckley has worked extensively to foster greater collaboration among CDC programs working on tickborne diseases, to enhance and integrate surveillance for tickborne diseases in partnership with states, and to facilitate applied research projects that address key public health questions regarding tickborne diseases. She holds a BS in Environmental Engineering from the University of Florida, and a PhD in Environmental Health from Colorado State University.

Public Information from the CDC and Medscape

Cite this: Southern Tick-Associated Rash Illness -- When a Bull's-Eye Rash Isn't Lyme Disease - Medscape - Mar 25, 2013.