Rocky Mountain Spotted Fever was first described from patients in the Rocky Mountain Region but is more prevalent in the Southeastern United States. A band from North Carolina to Oklahoma defines the states with the highest frequency of cases. It is primarily transmitted by the American Dog tick, Dermacentor variabilis. Other vectors are the Rocky Mountain wood tick Dermacentor andersoni, and brown dog tick Rhipicephalus sanguineus. Incidence of Rocky Mountain Spotted Fever varies from year to year with 2008 reports reaching an all time high.
Rocky Mountain Spotted Fever, caused by a bacterium, Rickettsia rickettsii. is the most dangerous of the tick borne diseases. Rickettsia rickettsii invades the muscles of the organs and may lead to organ failure. Before the development of modern antibiotics, Rocky Mountain Spotted Fever proved fatal in almost 70% of cases. To be most effective, an appropriate antibiotic should be given early in the diagnosis. Unfortunately, diagnosis is problematic. Rickettsia rickettsii infects tissues and is not carried in the blood until late stages of infection. As a result, blood tests early in the infection are typically false negatives. Once a rash appears, biopsies of the rash areas can be diagnostic. Signs such as antibodies pointing to Rocky Mountain Spotted Fever may not appear until a week or more. Early symptoms are similar to flu or strep throat. The characteristic rash can take more than a week to develop or fails to develop in 10% of patients. Thus many cases are misdiagnosed at first and are only accurately diagnosed on follow up visits.
Failure to properly diagnose and treat can lead to tragedy. In Summer 2017 in Indiana, a toddler died from Rocky Mountain Spotted Fever. The child probably received a tick bite on a camping trip and first symptoms appeared over one week later. The symptoms were misdiagnosed as virus or strep throat by doctors, but the symptoms worsened. After hospitalization, Rickettsia rickettsii was finally diagnosed but the infection had progressed such that anti-biotic treatment was not effective.
If experiencing a tick bite that is accompanied by a rash or the “summer flu” it is important to give the treating physician that information. Rocky Mountain Spotted Fever is difficult to detect and some physicians will administer doxycycline if it is suspected but unconfirmed. Fortunately, most tick bites do not result in infection. However prevention of tick bites through the use of repellents and avoiding tick habitats is a wise precaution.