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Rocky Mountain spotted fever

Definition

Rocky Mountain spotted fever (RMSF) is a disease caused by a type of bacteria carried by ticks.

Alternative Names

Spotted fever

Causes

RMSF is caused by the bacterium Rickettsia rickettsii (R Rickettsii), which is carried by ticks. The bacteria is spread to humans through a tick bite.

In the western United States, the bacteria are carried by the wood tick. In the eastern US, they are carried by the dog tick. Other ticks spread the infection in the southern US and in Central and South America.

Contrary to the name "Rocky Mountain," most recent cases have been reported in the eastern US. States include North and South Carolina, Virginia, Georgia, Tennessee, and Oklahoma. Most cases occur in the spring and summer and are found in children.

Risk factors include recent hiking or exposure to ticks in an area where the disease is known to occur. The bacteria are unlikely to be transmitted to a person by a tick that has been attached for less than 20 hours. Only about 1 in 1,000 wood and dog ticks carry the bacteria. Bacteria can also infect people who crush ticks they have removed from pets with their bare fingers. Not all people will remember getting a tick bite.

Symptoms

Symptoms usually develop about 2 to 14 days after the tick bite. They may include:

  • Chills and fever
  • Confusion
  • Headache
  • Muscle pain
  • Rash -- usually starts a few days after the fever; first appears on wrists and ankles as spots that are 1 to 5 mm in diameter, then spreads to most of the body. Some infected people don't get a rash.

Other symptoms that may occur with this disease:

Exams and Tests

The health care provider will perform a physical examination and ask about the symptoms.

Tests that may be done include:

Treatment

Treatment involves carefully removing the tick from the skin. To get rid of the infection, antibiotics such as doxycycline or tetracycline need to be taken. Pregnant women are usually prescribed chloramphenicol.

Outlook (Prognosis)

Treatment usually cures the infection. About 3% of people who get this disease will die.

Possible Complications

Untreated, the infection may lead to health problems such as:

  • Brain damage
  • Clotting problems
  • Heart failure
  • Kidney failure
  • Lung failure
  • Meningitis
  • Pneumonitis (lung inflammation)
  • Shock

When to Contact a Medical Professional

Contact your provider if you develop symptoms after exposure to ticks or a tick bite. The complications of untreated RMSF are often life threatening.

Prevention

When walking or hiking in tick-infested areas, tuck long pants into socks to protect the legs. Wear shoes and long-sleeved shirts. Ticks will show up on white or light colors better than on dark colors, making them easier to see and remove.

Remove ticks immediately by using tweezers, pulling carefully and steadily. Insect repellent may be helpful. Because far fewer than 1% of ticks carry this infection, antibiotics are not usually given after a tick bite.

Gallery

Rocky mountain spotted fever, lesions on arm
This is the appearance of the rash of Rocky Mountain Spotted Fever on the hands and forearms. The rash starts on the hands and feet and later spreads to the trunk. It is caused by a bacteria transmitted to humans by a tick bite. (Image courtesy of the Centers for Disease Control and Prevention.)
Lyme disease
Having a tick attached to your body isn't just getting a little too close to nature. The tick can make you seriously ill with Lyme disease. Lyme disease is caused by bacteria called Borrelia burgdorferi. Blacklegged ticks carry these bacteria. The ticks pick up the bacteria when they bite mice or deer that are infected with Lyme disease. You can get the disease if you are bitten by an infected tick, mostly in northeastern states and on the West Coast. The good news is that usually a tick has to be attached to your body for 24 to 36 hours to infect you. The bad news is that blacklegged ticks are so small they're almost impossible to see. Many people with Lyme disease never even see a tick on their body. But most people bitten by a tick do NOT get Lyme disease. So, how do you know for sure that you have Lyme disease? The flu-like symptoms of Lyme disease usually start days or weeks after you've been bitten. You might have Itching all over your body; Chills, fever, and light headedness; Or perhaps a Headache, muscle pain, and a stiff neck. You'll probably see a bull's eye rash on your body. It can get pretty big. After a few weeks, the muscles in your face might feel weak or even paralyzed. Your knees and other joints may swell and hurt. You might even notice your heart skipping some beats. Eventually, your muscles might move strangely, you may feel numbness or tingling, and you may start to have trouble speaking. A doctor will test your blood for antibodies that are trying to fight the bacteria in your blood. One of these tests is called the ELISA test, and you'll often have a second test called the Western blot test to confirm you have Lyme disease. To treat Lyme disease, you may need to take antibiotics for up to a month. Pain medicines from the drug store can help soothe your joint stiffness. If it's caught early, Lyme disease is pretty easily treated. Without treatment, you can have heart, muscle, and even nerve problems. So the next time you're out in the woods or high grass, wear protective clothing, and do check yourself for ticks once you get home.
Lyme disease
Having a tick attached to your body isn't just getting a little too close to nature. The tick can make you seriously ill with Lyme disease. Lyme disease is caused by bacteria called Borrelia burgdorferi. Blacklegged ticks carry these bacteria. The ticks pick up the bacteria when they bite mice or deer that are infected with Lyme disease. You can get the disease if you are bitten by an infected tick, mostly in northeastern states and on the West Coast. The good news is that usually a tick has to be attached to your body for 24 to 36 hours to infect you. The bad news is that blacklegged ticks are so small they're almost impossible to see. Many people with Lyme disease never even see a tick on their body. But most people bitten by a tick do NOT get Lyme disease. So, how do you know for sure that you have Lyme disease? The flu-like symptoms of Lyme disease usually start days or weeks after you've been bitten. You might have Itching all over your body; Chills, fever, and light headedness; Or perhaps a Headache, muscle pain, and a stiff neck. You'll probably see a bull's eye rash on your body. It can get pretty big. After a few weeks, the muscles in your face might feel weak or even paralyzed. Your knees and other joints may swell and hurt. You might even notice your heart skipping some beats. Eventually, your muscles might move strangely, you may feel numbness or tingling, and you may start to have trouble speaking. A doctor will test your blood for antibodies that are trying to fight the bacteria in your blood. One of these tests is called the ELISA test, and you'll often have a second test called the Western blot test to confirm you have Lyme disease. To treat Lyme disease, you may need to take antibiotics for up to a month. Pain medicines from the drug store can help soothe your joint stiffness. If it's caught early, Lyme disease is pretty easily treated. Without treatment, you can have heart, muscle, and even nerve problems. So the next time you're out in the woods or high grass, wear protective clothing, and do check yourself for ticks once you get home.
Rocky mountain spotted fever, lesions on arm
This is the appearance of the rash of Rocky Mountain Spotted Fever on the hands and forearms. The rash starts on the hands and feet and later spreads to the trunk. It is caused by a bacteria transmitted to humans by a tick bite. (Image courtesy of the Centers for Disease Control and Prevention.)
Lyme disease
The most common early sign of lyme disease is the appearance of a rash on the skin that looks like a bulls eye. The rash begins as a reddened area near the area of the tick bite. As the rash gets bigger, it clears in the center and develops a red ring around the outer perimeter. Other symptoms include muscle or joint aches, stiff neck, headache, weakness, fever, swollen lymph nodes and other flu-like symptoms.
Henoch-Schonlein purpura on the lower legs
Henoch-Schonlein Purpura. This disorder usually presents with red to purple bumps on the legs, often accompanied by aching in the joints and fever. This condition follows an infection and usually resolves without treatment. Skin lesions most commonly occur below the knee but may also be seen on the thigh, buttocks, and rarely on the arms.
Rocky mountain spotted fever, lesions on arm
This is the appearance of the rash of Rocky Mountain Spotted Fever on the hands and forearms. The rash starts on the hands and feet and later spreads to the trunk. It is caused by a bacteria transmitted to humans by a tick bite. (Image courtesy of the Centers for Disease Control and Prevention.)
Stomach
The stomach is the portion of the digestive system most responsible for breaking down food. The lower esophageal sphincter at the top of the stomach regulates food passing from the esophagus into the stomach, and prevents the contents of the stomach from reentering the esophagus. The pyloric sphincter at the bottom of the stomach governs the passage of food out of the stomach into the small intestine.

References

Blanton LS, Walker DH. Rickettsia rickettsii and other spotted fever group rickettsiae (Rocky Mountain spotted fever and other spotted fevers). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 186.

Bolgiano EB, Sexton J. Tickborne illnesses. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 126.

Last reviewed June 20, 2021 by Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team..

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