Rocky Mountain Spotted Fever

Overview

Rocky Mountain Spotted Fever is a reportable disease in Oklahoma.  Rocky Mountain Spotted Fever (RMSF) can be a potentially severe or fatal disease caused by the bacteria Rickettsia rickettsii (R. rickettsii). Humans nearly always become infected with the bacteria following the bite of an infected tick. In Oklahoma, the tick associated with transmission of R. rickettsii include the American dog tick (Dermacentor variabilis). The other known tick vectors of R. rickettsii include the Rocky Mountain wood tick (Dermacentor andersoni), brown dog tick (Rhipicephalus sanguineus), and the cayenne tick (Amblyomma cajennense). Tick bites due to the American dog tick are common in Oklahoma. Fortunately, only 1%-3% of the tick population will be infected and capable of transmitting R. rickettsii.

The symptoms of RMSF generally include a sudden onset of fever, myalgia, and headache within 3 to 14 days following a tick bite. A fine, bumpy, red rash often appears on the extremities and may quickly spread to the palms of the hands and soles of the feet, before spreading to other parts of the body. However, not all persons with RMSF develop a rash. Other common symptoms of RMSF include nausea, vomiting, and abdominal pain.

Treatment for RMSF with antibiotics (usually doxycycline) is very effective at reducing the severity of the disease. It is important that antibiotic treatment for RMSF be started without delay when RMSF is suspected. Overall, 3%-5% of persons with RMSF die due to the disease without prompt treatment with the appropriate antibiotics. Although RMSF can be severe, preventive antibiotic therapy in non-ill persons following a tick bite is not recommended.

Laboratory testing for RMSF typically consists of blood samples taken in the early stages of the illness (acute) and follow up (convalescent) specimens taken at least four weeks after the first specimen. Laboratory testing, though important, can take days to weeks for results to become available.

If RMSF is suspected, it is important treatment with the appropriate antibiotics not be delayed while waiting for laboratory confirmation.

Please visit the following links for information and  tips on preventing tick bites and safe tick removal.

ADS Resources:
Rocky Mountain Spotted Fever Fact Sheet  En Espanol
Tickborne Disease Prevention

Other Resources:
CDC RMSF

Surveillance Resources:
Rocky Mountain Spotted Fever Summary