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Rocky Mountain Spotted Fever
What is Rocky Mountain spotted fever?
Who is at risk?
- RMSF is the deadliest tick-borne disease in the U.S.
- It is spread by several ticks in the U.S. including the American dog tick, Rocky Mountain wood tick, and the brown dog tick (parts of the SW U.S. and Mexico).
- Anyone living or recreating where these ticks are present may be at risk.
- Rocky Mountain spotted fever has been diagnosed throughout the U.S., however cases are most commonly reported from North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma.
- Children under 10 years old, American Indians, people with a compromised immune system, and people with delayed treatment are at an increased risk of fatal outcome from RMSF.
- The majority of cases reported have an illness onset during the months of June and July. However, the seasonality varies for different regions of the country.
Signs and Symptoms
What are the signs and symptoms of RMSF?
- Early symptoms can be non-specific, including fever and headache, but can rapidly progress and become life threatening.
- See your healthcare provider if you become ill after a tick bite or having been in the brushy or woodsy areas where ticks commonly live.
- The first symptoms of Rocky Mountain spotted fever (RMSF) typically begin 2-14 days after the bite of an infected tick.
- The disease is characterized by acute fever, headache, muscle pain, vomiting, and general discomfort.
- A rash may also develop 2-4 days after the fever begins and often spreads with time.
- Approximately 90% of infected individuals will develop some type of rash, however, the rash may not develop until later in the disease process.
- RMSF can be life-threatening, but early treatment with doxycycline can prevent disability and death.
- Some patients who survive RMSF can be left with long term health effects including neurological deficits, damage to internal organs, and vascular damage requiring amputation of some extremities.
Diagnosis and Testing
How is RMSF diagnosed?
- Early symptoms of RMSF may resemble other diseases.
- Diagnostic tests, especially those based on the detection of antibodies, will often appear negative for the first 7-10 days of illness.
- The diagnosis of RMSF is based on clinical suspicion alone.
- Treatment is most effective at preventing death if started in the first five days of symptoms.
- The diagnosis must be made and treatment initiated based on clinical signs and symptoms, and can later be confirmed using specialized confirmatory laboratory tests.
- Rickettsial Disease Testing and Interpretation
What should I do if I have a tick that I want to identify?
- Knowing what kind of tick bit you may be important in knowing what your risk of disease is.
- The Michigan Department of Health and Human Services (MDHHS) provides tick identification at no charge to Michigan citizens.
- There are two ways to have a tick identified, 1) By submitting a photo of your tick, or, 2) by sending the tick to the MDHHS for microscopic identification.
- If you want to submit a photo of your tick, the MDHHS will make all attempts to identify the tick based on the condition of the tick and the condition of the photos.
- Definitive tick identification may only be made by sending the tick for microscopic examination.
RMSF information for clinicians
The Michigan Department of Health and Human Services Bureau of Laboratories can assist Michigan healthcare providers with RMSF diagnostic testing:
What is the treatment for RMSF?
Treatment should never be delayed pending the receipt of laboratory test results, or be withheld on the basis of an initial negative finding.
- The antibiotic doxycycline is the first line treatment for adults and children of all ages and should be initiated immediately whenever RMSF is suspected.
- Treatment is most effective at preventing severe complications, including death, if started within the first 5 days of symptoms.
- Treatment should continue for at least 3 days after the fever subsides and there is evidence of improvement for a minimum of 5-7 days.
Educational Materials and Guidance Documents
- Ticks and Your Health - Brochure describing Lyme disease and other tick-borne diseases in Michigan. Other topics covered include tick-bite prevention, preventing ticks on pets, and landscape techniques to minimize tick risk.
- Michigan's Five Most Common Ticks
- Michigan Tick ID Card - Pocket-sized card for identifying common ticks in Michigan. Information regarding tick removal and tick-bite prevention.
Centers for Disease Control and Prevention Resources
For the Public
- Tick Removal
- What To Do After a Tick Bite - Ticks are significant vectors (carriers) of pathogens that cause human and animal disease. In Michigan, tick-borne diseases are rare, but they do occur and can be serious if not properly diagnosed and treated.
- Hunter Safety: It's Open Season on Ticks
For Healthcare Providers
- Tickborne Diseases of the U.S.
- Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis - A Practical Guide for Health Care and Public Health Professionals
- RMSF: Tools for healthcare providers
- Research on doxycycline and tooth staining
Data and Statistics