Southern Tick-Associated Rash Illness

In the late 1980s and 1990s, physicians in the southeastern and south central United States began to recognize individuals who developed a rash essentially identical to erythema migrans, the typical earliest stage of Lyme disease, but did not develop other manifestations of that infection. The rash was found to be associated with the bite of the lone star tick, Amblyomma americanum.

This simulator of Lyme disease has been named Southern tick-associated rash illness (STAR Illness or STARI). It also is known as Masters disease because Edwin Masters, a family physician in private practice in Cape Girardeau, Missouri, reported forty-five persons with the disorder in 1991.

Symptoms and Diagnosis: The typical clinical finding is a roughly circular erythematous rash centered on the site of the tick bite. Central clearing may be present. Investigators emphasize that the rash is essentially identical to erythema migrans.

Other symptoms that may be present include fatigue (50 percent), headache (43 percent), muscle stiffness including stiff neck (36 percent), and fever (29 percent). However, signs and symptoms of the second or third stages of Lyme disease do not ensue, even in patients who are not treated.

No specific laboratory studies are available. Significantly, no serologic evidence of infection by Borrelia burgdorferi, the agent that causes Lyme disease, can be found.

The Causative Organism: Spirochetes have been seen in lone star ticks with microscopy, and a spirochete has been detected by DNA analysis and given the name Borrelia lonestari. However, attempts to culture the spirochete have consistently failed. Modified Barbour-Stoenner-Kelly (BSK) media, the best medium for cultivating the Lyme disease spirochete B. burgdorferi, is apparently not suitable for cultivating this organism.

Although B. lonestari is widely accepted as causative, not everyone has endorsed this etiology, particularly Lyme disease advocacy groups that consider Lyme disease to be more widespread than generally recognized. Masters and others have pointed out that although Lyme disease serology results were often negative, the results frequently differed from the results in control individuals without Lyme disease.

In 2001, an individual exposed to ticks in Maryland and North Carolina developed a rash indistinguishable from erythema migrans after an A. americanum tick bite. DNA typical of B. lonestari was identified in a skin biopsy taken at the leading edge of the rash and in the tick, which had been removed by the individual’s physician. Serologic testing for Lyme disease was negative.

However, Masters reportedly has had tissue samples from “hundreds” of individuals tested for B lonestari without finding typical DNA in any of them.

The Vector: Lone star ticks, Amblyomma americanum, are numerous throughout the southeast United States from central Oklahoma and Texas to the coast and northward into Maine. Their life cycle and ecologic requirements are similar to Ixodes ticks.

Distribution of Lone Star Ticks

(Amblyomma americanum)

All three stages—larval, nymph, and adult—aggressively bite people. However, live spirochetes are observed in only 1 to 3 percent of these ticks.

Adult Female Lone Star Tick

(The white spot in the center of the

back is responsible for the name.)

More pictures, including size comparisons, available at ent.iastate.edu/imagegal/ticks

Therapy: Because the organism has not been cultured, conventional controlled studies of therapy have not been carried out. Individuals with the rash have been given a variety of antibiotics, most commonly doxycycline. The treatment has been successful, but the rash and other symptoms disappear without therapy.

Serologic testing for Lyme disease may be advisable. Until the results are received, doxycycline therapy, which is effective in the early stages of that infection, appears reasonable. However, Lyme disease is uncommon in most of the area where lone star ticks are found.

Investigational Studies: CDC is conducting studies of this disorder under an Institutional Review Board-approved investigational protocol. Investigators would like to obtain blood and urine samples and 2 mm skin punch biopsies from appropriate patients. Physicians who encounter individuals in southeast or south central states who develop a red, expanding rash 5 cm or more in diameter up to fourteen days after a bite by a lone star tick communicate are requested to communicate with one of the investigators at the Bacterial Zoonoses Branch, P.O. Box 2087, Fort Collins, CO 80522-2087. The investigators are Ned Hayes (970-221-6474, ebh2@cdc.gov), Barbara Johnson (970-221-6463, bij1@cdc.gov), and David Dennis (970-221-6476, dtd1@cdc.gov). (FAX 970-221-6476.)

Instructions for obtaining specimens, shipping under the CDC Federal Express account number, and patient consent forms are available from the Florida Department of Health http://www.doh.state.fl.us/disease_ctrl/epi/htopics/popups/lyme.htm