Michelle Badash, MS
Rocky Mountain spotted fever (RMSF) is a severe infectious disease that affects your blood vessels. It is potentially fatal.
The disease is spread by ticks in North, Central, and South America.
RMSF is caused by a specific bacteria. This bacteria is carried by the American dog tick and the Rocky Mountain wood tick. It passes to humans when an infected tick bites the skin. The bacteria can then pass into the bloodstream.
The bacteria sits in the lining of small blood vessels and multiplies. The growth of the bacteria causes irritation and swelling in the blood vessels. Blood and other fluids can then leak out of the blood vessels into the surrounding tissue.
Factors that increase your chance of RMSF include:
The first symptoms of RMSF often occur within 2-14 days after a tick bite and may include:
Most but not all people with RMSF develop a rash. The rash begins as small, flat pink spots but can later progress to red-purple spots. The rash most often starts on the wrists, forearms and ankles.
If left untreated, RMSF can cause severe problems to organs or skin near the leaky blood vessels. Symptoms will depend on what organs are involved.
The doctor will ask about your symptoms and medical history. A physical exam will be done. RMSF can be difficult to diagnose because the symptoms are similar to many other diseases and the rash may not be there at first. Many people do not realize they have been bitten by a tick which can also make the diagnosis more difficult.
A blood test may be done to confirm the diagnosis if your doctor suspects RMSF. Other tests, like a complete blood count and electrolytes, may be done to evaluate the severity of the disease. A spinal tap may be done to look for infection in the spinal fluid.
Treatment may be started before a clear diagnosis is made based on your risk and fever.
RMSF is treated with antibiotics. Doxycyline is the drug of choice, but others may be chosen if necessary. It is important to start this
early. Make sure to take all of your medication as recommended. Do not stop taking the medication once you feel better, unless your doctor says it is safe to do so.
The best way to prevent RMSF is to limit your exposure to ticks. If you live in an area that is prone to ticks, take the following precautions:
Centers for Disease Control and Prevention (CDC)
National Library of Medicine
Canadian Family Physician
Public Health Agency of Canada
Rocky Mountain spotted fever. Centers for Disease Control and Prevention (CDC) website. Available at: http://www.cdc.gov/rmsf/. Updated April 30, 2012. Accessed May 21, 2013.
Rocky mountain spotted fever. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed/what.php. Updated April 10, 2013. Accessed May 21, 2013.
Last reviewed December 2013 by David L Horn, MD, FACP
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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