Definition

Rocky Mountain spotted fever is an infectious disease caused by bacteria carried by ticks.

Alternative Names

Causes, incidence, and risk factors

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

In the western United States, the bacteria is carried by the wood tick, and in the eastern U.S. it is carried by the dog tick. However, 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 with about 1,000 cases reported per year. Most of the reported cases have been in children.

Risk factors include recent hiking or exposure to ticks in an area where the disease is known to occur.

Symptoms

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

• Chills
• Fever
• Severe headache
• Muscle pain
• Mental confusion
• Rash -- usually starts a few days after the fever; first appears on wrists and ankles, then spreads to most of the body; some people do not get a rash

Additional symptoms that may be associated with this disease:

• Abnormal sensitivity to light
• Diarrhea
• Excessive thirst
• Hallucinations
• Loss of appetite
• Nausea
• Vomiting

Signs and tests

Tests that may be done include:

• Antibody titer by complement fixation or immunofluorescence
• Kidney function tests
• Platelet count
• Partial thromboplastin time (PTT)
• Prothrombin time (PT)
• Red blood cell count
• Skin biopsy taken from the rash to check for R. rickettsii
• Urinalysis to check for blood in the urine and protein in the urine

Treatment

Treatment involves careful removal of the tick from the skin and antibiotics to eliminate the infection. Doxycycline or tetracycline are frequently used. Chloramphenicol may be used in pregnant women.

Note: Tetracycline and doxycycline pills are usually not prescribed for children until after all the permanent teeth have come in. These medicines can permanently discolor teeth that are still forming. For this disease, it may be used for short periods of time when it is felt that the benefits outweigh the risks.

Support Groups

Expectations (prognosis)

Treatment usually cures the infection. Complications are rare but can include paralysis, hearing loss, nerve damage, and, rarely, death.

Complications

• Brain damage
• Clotting problems
• Kidney failure
• Heart failure
• Lung failure
• Meningitis
• Pneumonitis
• Shock

Calling your health care provider

Call your health care provider if symptoms develop after exposure to ticks or known tick bite. The complications of untreated Rocky Mountain spotted fever can be life threatening.

Prevention

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

Remove ticks immediately by using a tweezers, pulling carefully and steadily. Insect repellent may be helpful. Because less than 1% of ticks carry this infection, antibiotics are not usually given after a tick bite if there is no evidence of disease.

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