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Rocky Mountain spotted fever (RMSF) is a severe 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:

• Being outdoors in areas known to have RMSF especially from April to September
• Exposure to tick-infested areas such as long grass, weeds or low brush
• Exposure to dogs
• Not using preventative steps (listed below)

The first symptoms of RMSF often occur within 2-14 days after a tick bite and may include:

• Fever
• Rash
• Nausea
• Vomiting
• Muscle pain
• Lack of appetite
• Headache
• Red eyes

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 pots. 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.

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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. 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.

Treatment may be started before a clear diagnosis is made based on your risk and fever.

RMSF is treated with antibiotics. It is important to start this treatment 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:

• Wear light-colored clothing. This makes ticks are more visible.
• Tuck pant legs inside socks. This stops ticks from crawling up under your pants.
• Apply insect repellents containing DEET (applied to exposed skin). Apply permethrin to clothing.
  • For young children, DEET should be avoided or used sparingly. Carefully follow the directions on the label.
• Carefully check your entire body for ticks after returning from outdoor areas.
• Check pets for ticks.