Lone star tick a concern, but not for Lyme disease

Many people, even health care providers, can be confused about whether the lone star tick causes Lyme disease. It does not. Patients bitten by lone star ticks will occasionally develop a circular rash similar to the rash of early Lyme disease. The cause of this rash has not been determined; however, studies have shown that the rash is not caused by Borrelia burgdorferi, the bacterium that causes Lyme disease.

This condition has been named southern tick-associated rash illness (STARI). The rash may sometimes be accompanied by fatigue, headache, fever, and muscle pains. In the cases of STARI studied to date, the rash and accompanying symptoms have resolved following treatment with an oral antibiotic (doxycycline), but it is unknown whether this medication speeds recovery. STARI has not been linked to arthritis, neurologic disease, or chronic symptoms. Researchers once hypothesized that STARI was caused by the spirochete, Borrelia lonestari, however further research did not support this idea. The cause of STARI remains unknown.

The lone star tick, Amblyomma americanum, is found throughout the eastern, southeastern and south-central states. The distribution, range and abundance of the lone star tick have increased over the past 20-30 years, and lone star ticks have been recorded in large numbers as far north as Maine and as far west as central Texas and Oklahoma. All three life stages (larva, nymph, adult) of the lone star tick will feed on humans, and may be quite aggressive. Lone star ticks will also feed readily on other animals, including dogs and cats, and may be brought into the home on pets. The saliva from lone star ticks can be irritating; redness and discomfort at a bite site does not necessarily indicate an infection.

People should monitor their health closely after any tick bite, and should consult their physician if they experience a rash, fever, headache, joint or muscle pains, or swollen lymph nodes within 30 days of a tick bite. These can be signs of a number of tickborne diseases.

Tick-borne illness may be prevented by avoiding tick habitat (dense woods and brushy areas), using insect repellents containing DEET or permethrin, wearing long pants and socks, and performing tick checks and promptly removing ticks after outdoor activity. Additional prevention tips are available.

In a study that compared physical findings from STARI patients in Missouri with Lyme disease patients in New York (Wormser et al, 2005), several key differences were noted:

• Patients with STARI were more likely to recall a tick bite than were patients with Lyme disease.
• The time period from tick bite to onset of the skin lesion was shorter among patients with STARI (6 days, on average).
• STARI patients with an erythema migrans rash were less likely to have other symptoms than were Lyme disease patients with erythema migrans rash.
• STARI patients were less likely to have multiple skin lesions, had lesions that were smaller in size than Lyme disease patients (6-10 cm for STARI vs. 6-28 cm for Lyme disease), and had lesions that were more circular in shape and with more central clearing.
• After antibiotic treatment, STARI patients recovered more rapidly than did Lyme disease patients.

The rash of STARI is a red, expanding “bull’s-eye” lesion that develops around the site of a lone star tick bite. The rash usually appears within 7 days of tick bite and expands to a diameter of 8 centimeters (3 inches) or more. The rash should not be confused with much smaller areas of redness and discomfort that can occur commonly at the site of any tick bite. Patients may also experience fatigue, headache, fever, and muscle pains. The saliva from lone star ticks can be irritating; redness and discomfort at a bite site does not necessarily indicate an infection.

STARI is diagnosed on the basis of symptoms, geographic location, and possibility of tick bite. Because the cause of STARI is unknown, no diagnostic blood tests have been developed. Researchers once hypothesized that STARI was caused by the spirochete, Borrelia lonestari; however, further research did not support this idea.

It is not known whether antibiotic treatment is necessary or beneficial for patients with STARI. Nevertheless, because STARI resembles early Lyme disease, physicians will often treat patients with oral antibiotics.

STARI is specifically associated with bites of Amblyomma americanum, known commonly as the lone star tick. 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. The adult female is distinguished by a white dot or “lone star” on her back. All three life stages of A. americanum aggressively bite people.