Southern tick-associated rash illness (STARI)

INTRODUCTION

During the 1980s, physicians in Missouri and the southeastern United States described a new illness characterized by the presence of a rash typical of erythema migrans (EM) and mild flu-like symptoms that was temporally associated with a bite by the Lone Star tick (Amblyomma americanum) (picture 1). EM-like skin lesions appeared at the site of these tick bites, but serologic tests in such patients consistently failed to show evidence of infection with Borrelia burgdorferi, a finding that fits with the fact that the vector for Lyme disease (Ixodes scapularis) (picture 2) was unknown or uncommon in these locations [1,2]. Experimental studies subsequently revealed that A. americanum is an incompetent vector for B. burgdorferi sensu stricto, the sole cause of Lyme disease in the United States [3]. (See "Microbiology and epidemiology of Lyme disease".)

Over the next 20 years, this illness was given a variety of names, including Southern Lyme disease and Masters' disease. The most widely used name, Southern tick-associated rash illness (STARI), may be misleading since this syndrome and its presumed vector is now known to occur in other regions such as the Midwest and the mid-Atlantic states.

The putative causative agent of this disease, Borrelia lonestari, has never been isolated from a human with STARI, and Koch's postulates have not yet been fulfilled in experimental studies. Nevertheless, STARI is widely presumed to be caused by B. lonestari and to be transmitted to humans by the Lone Star tick.

Numerous questions remain unanswered about the spectrum of clinical features and the pathophysiology of human illness following exposure to B. lonestari. In addition, the nature of its intermediate vertebrate host(s), the geographic range of illness, and the most effective treatment for STARI are unknown or incompletely understood.

At present, STARI should be considered to be a syndrome of unproven cause that is clinically diagnosed on the basis of its characteristic skin rash, mild clinical course, and occurrence in areas where Lyme disease is either uncommon or not present, but where A. americanum ticks are known to be present. Until there is a definitive diagnostic test for this illness and until the causative organism has been definitively isolated from humans, much of our understanding about epidemiology, clinical features, and treatment will remain speculative.