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Rocky Mountain spotted fever

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

Causes

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

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

Contrary to the name "Rocky Mountain," most recent cases have been reported in the eastern United States, including North and South Carolina, Virginia, Maryland, Georgia, Tennessee, and Oklahoma. Most cases occur in the spring and summer.  Most of the cases have been 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.

Symptoms

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

  • Chills
  • Confusion
  • Fever
  • 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. About one-third of infected people do not get a rash.

Other symptoms that may occur with this disease:

Exams and Tests

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

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

When to Contact a Medical Professional

Call your health care provider if you develop symptoms after exposure to ticks or a tick bite. The complications of untreated Rocky Mountain spotted fever are often life-threatening.

Prevention

When walking or hiking in tick-infested areas, tuck long pants into socks to protect the legs. ear 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.

Alternative Names

Spotted fever

References

Traub SJ, Cummins GA. Tick-borne diseases. In: Auerbach PS. Wilderness Medicine. 6th ed. Philadelphia, Pa.: Elsevier Mosby; 2011:chap 51.

Walker DH. Rickettsia rickettsii and other spotted fever group rickettsiae (rocky mountain spotted fever and other spotted fevers). In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa.: Elsevier Churchill-Livingstone; 2009:chap 187.

Update Date: 5/19/2013

Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

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