Arizona: Rocky Mountain Spotted Fever 2003-2005

2003-2005 Highlights, Vector-Borne and Zoonotic Disease Newsletter, Arizona Department of Health Services

Rocky Mountain Spotted Fever (RMSF) has emerged as a major concern in portions of Arizona. Prior to 2004, only eight cases of RMSF had been recorded in the state. In 2004 alone, 15 cases were reported. Another 13 were added in 2005. All of the 2004-2005 cases occurred in mountainous east-central Arizona and appear to be associated with the brown dog tick, Rhipicephalus sanguineus, a species not previously known to be a vector in the U.S. It is thought that the brown dog tick, while not an efficient vector, can transmit RMSF under certain conditions, namely when the number of ticks in a community is large and dogs are allowed to roam freely. Therefore, controlling ticks on dogs and around the home as well as enforcement of animal control regulations are essential steps in preventing RMSF. A very unfortunate aspect of the current outbreak is that it has disproportionately affected children. From 2003-2005, five individuals have died from RMSF infections. RMSF, caused by Rickettsia rickettsii bacteria, is an acute febrile illness typically marked by the sudden onset of moderate to high fever with a rash forming a few days later on the extremities and spreading to the palms and soles and then the torso. Severe headache and muscle aches are also common symptoms. In some cases, infection with R. rickettsii does not produce classic symptoms. Lack of appearance of rash and/or other typical symptoms can delay diagnosis and treatment. A sweeping multi-agency RMSF response effort was undertaken in 2005 and more work is planned for 2006. Because of this recent activity, RMSF should be included in the differential diagnosis for Arizona care providers seeing patients with unexplained rash and fever illnesses. Ticks removed from patients may be submitted to ADHS-Vector for identification.