Rickettsia parkeri infection is a spotted fever transmitted principally by the Gulf Coast tick (Amblyomma maculatum). Clinical manifestations are similar but relatively less severe than those of Rocky Mountain spotted fever. The disease manifests as a mild febrile illness accompanied by headache, fatigue, myalgias, arthralgias, and a rash consisting of eschars, erythematous papules, and macules. Symptoms occur approximately one week after a tick bite.

The disease is seen where A. maculatum resides, which is predominantly in regions that border the Gulf of Mexico and the Atlantic Ocean. The Gulf Coast tick is also found in some regions of Central America, South America, and the Caribbean. In Uruguay and Argentina, cases have been attributed to Amblyomma triste and Amblyomma tigrinum. In 2014-2015, one confirmed and one probable case were identified in southern Arizona, with transmission attributed to A. triste.

Tick exposure increases with participation in outdoor activities in grassy areas during April through September and contact with household dogs and cats. Many patients will not recall a tick bite, as the bite is typically painless and the body location of the bite may be obscure.