Increases in Rocky Mountain spotted fever detected in Arizona

A March 30 email from the Arizona Health Alert Network reports:

Arizona Department of Health Services has detected increased levels of Rocky Mountain spotted fever (RMSF) in the state including one confirmed and one suspect fatality. RMSF is a serious illness that can be fatal if not treated promptly and correctly, even in previously healthy people. Doxycycline is the treatment of choice for adults and children of all ages and should be initiated immediately whenever RMSF is suspected. Use of antibiotics other than doxycycline is associated with a higher risk of fatal outcome. Treatment is most effective at preventing death if doxycycline is started in the first 5 days of symptoms.

Treatment should never be delayed pending the receipt of laboratory test results, which are unlikely to be available in time for treatment to prevent death. Treatment should not be withheld in a patient where there is clinical suspicion on the basis of an initial negative finding for R. rickettsii. The diagnosis of RMSF must be made based on clinical signs and symptoms, and can later be confirmed using paired sera.

Most people will develop symptoms one week following the tick bite (range 3-14 days) and not all infected patients recall a tick bite.

RMSF usually presents with:

• Acute onset of fever
• Severe headache or other neurologic signs
• Malaise and severe myalgia
• Nausea/vomiting/diarrhea
• A macular or maculopapular rash appearing within 4-7 days following onset of symptoms, often present on the palms and soles; may be followed by a petechial rash on ~ day 6

Tick trapping in RMSF endemic areas indicates that the tick population is large and active at this time. RMSF should be considered in the differential diagnosis of febrile patients who reside in, or visit, tribal lands or are transferred from an Indian Health Service facility. It is important to note that few people with the disease will develop all symptoms and the number and combination of symptoms varies significantly from person to person. For example, in Arizona cases, 77% had any rash, 63.5% had fever documented, and 36.8% recounted a tick exposure

RMSF is a reportable condition in Arizona. In total, there have been six probable and confirmed RMSF cases reported in Arizona in 2012. Suspected cases should be reported to local health officials. Serologic testing is available at the Arizona State Public Health Laboratory (ASPHL), and paired sera collected 2-4 weeks apart are necessary to confirm or rule-out RMSF infection. The tests can be ordered using the ASPHL Microbiology Submission Form and selecting the “Rickettsial Spotted Fever” test from the Rickettsial IFA panel. Specimen collection guidelines can be found in the February 2012 Guide to Laboratory Services: Microbiology.
Specimens can be sent to:

Arizona State Health Laboratory
250 North 17th Avenue
Phoenix, AZ 85007

For more information on RMSF, contact your local health jurisdiction or ADHS Vector-Borne and Zoonotic Diseases staff at (602) 364-3676. You can also visit the ADHS RMSF and CDC RMSF websites.