A Guide to Rocky Mountain Spotted Fever (RMSF)

Rocky Mountain spotted fever (RMSF) is an illness caused by bites from ticks carrying the Rickettsia rickettsii (R. rickettsii) bacterium. The condition can cause severe symptoms like high fevers and tissue death. Prompt treatment is the best way to avoid serious complications. This article discusses the causes, symptoms, diagnosis, and treatments for Rocky Mountain spotted fever. It also covers the outlook for people with the condition, potential complications, and prevention.

RMSF is caused by infection with the R. rickettsii bacterium. This bacterium usually spreads through tick bites, particularly Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source the American dog tick, brown dog tick, and Rocky Mountain wood tick.

When the bacterium enters the body, it travels through the bloodstream and lymphatic vessels and multiplies, causing damage and widespread symptoms.

Learn what a tick bite looks like and what to do.

RMSF symptoms can include:

• fever that can reach 104°F (40°C)
• chills
• fatigue
• rash that may look Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source like splotches or dots
• nausea
• vomiting
• stomach pain
• headache
• muscle pain
• appetite loss

The symptoms of RMSF typically become apparent 4–10 days Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source after exposure to the bacterium. Some people may also experience:

• confusion
• insomnia
• liver inflammation
• heart issues
• tissue death
• coma

To diagnose RMSF, doctors will ask about your travel history, symptoms, and if you’ve had any tick bites. If a rash is present, they can order a skin biopsy. Taking a small tissue sample can allow doctors to determine whether bacteria are present.

Certain blood tests may also be useful, but the results may take weeks to arrive. If you are showing clinical signs of RMSF, your doctor may decide to start treatment before knowing the test results. Delaying treatment could result in severe complications.

Antibiotics are the main treatment for RMSF, with doxycycline (Vibramycin, Oraxyl) being the preferred drug Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source . The usual course of antibiotics lasts about 7–10 days, with the fever starting to fade within 3 days.

People with severe RMSF may require hospitalization for IV fluids, which are fluids administered through a vein.

With prompt treatment, the outlook for people with RMSF is favorable, and most people make a full recovery. Without treatment, outcomes can be much worse. Researchers estimate that RMSF has a mortality rate as high as 20–30% Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source without prompt antibiotic therapy.

If you are experiencing any concerning symptoms, such as a sudden fever or severe headache contact your doctor right away. It’s especially important to seek prompt medical care if these symptoms arise after a tick bite.

The Centers for Disease Control and Prevention (CDC) Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source notes that RMSF does not cause long-term infection. However, severe illness may result in complications. These include:

• arm, leg, or digit amputation due to blood vessel damage
• paralysis
• intellectual disability
• hearing loss

Some people may also experience encephalitis (brain inflammation), and heart and lung conditions.

People living in the same areas as the ticks that can transmit RMSF have an increased risk of contracting the illness. While anyone in the United States can get it, the CDC states that RMSF cases most commonly occur Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source in:

• Arkansas
• Missouri
• North Carolina
• Oklahoma
• Tennessee

While there is no vaccine available to prevent RMSF, you may be able to lower your risk of contracting the illness by protecting yourself from ticks. To do so, you can:

• Wear long-sleeved shirts and tuck your pants into your socks or boots.
• Avoid going into high grass or brush. If you can, stay on trails or paths.
• Apply 0.5% permethrin Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source , an insecticide, to your clothes. Do not apply it to your skin.
• Treat your skin with an insect repellent containing ingredients such as:
  • diethyltoluamide (DEET)
  • picaridin
  • oil of lemon eucalyptus (OLE)
  • para-menthane-diol (PMD)
  • 2-undecanone
  • IR3535, or ethyl butylacetylaminopropionate

Children under 3 years old should not use products containing PMD or OLE.

Check your clothing and body for ticks after being outside and shower within a few hours of coming inside. If you do get bitten by a tick, try to remove it carefully without crushing it. If you notice any symptoms after being bitten, contact your doctor.

These are a few other common questions about RMSF. Michaela Murphy, P.A.-C., reviewed the answers.

With antibiotic treatment, the fever associated with RMSF typically starts to improve within 3 days. Other symptoms may last longer. The course of antibiotics is usually 7–10 days long.

Rocky Mountain spotted fever is not contagious, meaning person-to-person transmission doesn’t occur. Infected ticks transmit it to people through their bites.

No, Lyme disease and RMSF are two different infections. However, they can both spread through tick bites. Lyme disease involves a different bacterium and can cause similar symptoms, including fever, headache, and muscle pain. Many people may also develop a “bull’s-eye” rash where the bite occurred.

Learn 8 things to know about Lyme disease.

People with severe RMSF may require hospitalization to receive IV fluids or more intensive treatment.

RMSF is a bacterial illness transmitted through tick bites. Without treatment, it can cause severe complications and even death.

If you are experiencing symptoms consistent with RMSF, whether or not you have noticed a tick bite, contact your doctor. Prompt antibiotic treatment is the best way to resolve the illness and prevent complications.