Southern Tick-Associated Rash Illness

A rash similar to the rash of Lyme disease has been described in humans residing in southeastern and south-central states and is associated with the bite of the lone star tick, Amblyomma americanum. This Lyme disease-like rash has been named Southern tick-associated rash illness (STARI).

Vector:

Amblyomma americanum ticks are found through the southeast and south-central states. Their life cycle and ecologic requirements are similar to Ixodes ticks with minor exceptions not described here. All three life stages of A. americanum aggressively bite people in the southern U.S. Research indicates that live spirochetes are observed in only 1-3% of A. americanum.

The Bacterium:

Even though spirochetes have been seen in A. americanum ticks by microscopy, attempts to culture it in the laboratory have consistently failed. Modified BSK (Barbour-Stoenner-Kelly) is the best medium for cultivating the Lyme disease spirochete, B. burgdorferi, but is apparently not suitable for cultivating the spirochete found in A. americanum. However, a spirochete has been detected in A. americanum by DNA analysis and was given the name Borrelia lonestari.

Symptoms and Diagnosis:

Persons living or travelling in southeast or southcentral states who develop a red, expanding rash with central clearing (the rash of Lyme disease, erythema migrans) following the bite of the lone star tick, A. americanum, should see their physician. The Centers for Disease Control and Prevention is interested in obtaining samples from such patients under an Institutional Review Board-approved investigational protocol.

Epidemiology and Risk:

In 2001, a patient with evidence of B. lonestari infection was reported in the medial literature. This patient had exposure to ticks in Maryland and North Carolina and developed a rash indistinguishable from erythema migrans after an A. americanum tick bite. DNA analysis indicated the presence of B. lonestari in a skin biopsy taken at the leading edge of the rash and in the tick removed by the physician. Serologic testing for Lyme disease was negative. The patient was treated with an oral antibiotic and returned to normal health.

Lone star ticks can be found from central Texas and Oklahoma eastward across the southern states and along the Atlantic coast as far north as Maine. Although several studies have demonstrated that 1-3% of these ticks are infected with a spirochete, a thorough assessment of risk of infection has not been conducted.

Prevention and Treatment:

Prevention measures similar to those for the Lyme disease vector will reduce your exposure to infected ticks:

• avoid tick habitats,
• reduce tick abundance,
• use personal protection equipment, and
• check and remove ticks.

In most circumstances, treating persons who only have a tick bite is not recommended. Individuals who are bitten by any tick should remove the tick and seek medical attention if any signs and symptoms of early Lyme disease, Lyme disease-like illness (STARI), ehrlichiosis, babesiosis, or tularemia develop over the ensuing days or weeks.