The identity of the causative organism of STARI is unknown. It has been called "seronegative Lyme disease" or "Southern Lyme disease." The CDC considers it one of the most obtuse clinical entities.
STARI is transmitted by the lone star tick, Amblyomma americanum. The range of this tick has expanded over the last three decades from East Texas and Eastern Oklahoma up to Maine, as shown in the image to the right. Larva, nymph, and adult ticks can aggressively feed on humans and other animals. These ticks can be brought into the home on dogs and cats.
The saliva is irritating, so redness and pain do not necessarily indicate disease. People are more likely to remember an A. americanum bite than Ixodes scapularis, the Lyme disease vector.