Rocky Mountain spotted fever (RMSF) is a bacterial infection that's transmitted to people by tick bites. It occurs most often in the spring and summer, during months when ticks are active — between April and early September.
Although RMSF is most common in the southeastern part of the United States (Virginia, Georgia, and the Carolinas), it occurs in other states as well. It's relatively rare (about 250 to 2,000 cases per year in the United States), but can be a serious disease if not treated properly.
The bacteria Rickettsia rickettsii that causes RMSF is transmitted by the dog tick (Dermacentor variabilis) in the eastern United States and by the wood tick (Dermacentor andersoni) in the Rocky Mountain states. On the West Coast, the lone star tick (Amblyomma americanum) also can transmit the bacteria.
RMSF gets its name from the trademark rash it causes — small red spots and blotches that begin on the wrists, ankles, palms, and soles. In addition to the rash, the infection can cause fever, chills, muscle aches, vomiting, and nausea. Typically, RMSF is treated with antibiotics and patients recover without any complications. But with late or no treatment, RMSF can cause serious health problems.
If your child has fever, achiness, stiff neck, or rash and has or may have been bitten by a tick, it's important to talk with your doctor.
Signs and Symptoms
The symptoms of RMSF typically develop within 1 week of a tick bite but can take up to 2 weeks to appear. In many cases, the person doesn't even remember being bitten by a tick.
Symptoms of RMSF usually begin suddenly. There is a high fever — often 103º-105ºF (39º-40ºC) — with chills, muscle aches, and a severe headache. Eyes can become red, muscles may feel tender, and there may be abdominal pain, nausea, vomiting, poor appetite, and fatigue.
The trademark rash of this infection can begin anytime up to 10 days after the fever and headache start, but it most often appears on the third to fifth day. The rash looks like small red spots or blotches that begin on the wrists, ankles, palms, and soles. It spreads up the arms and legs toward the trunk.
As the RMSF infection progresses, the original red spots might start to look more like bruises or bloody dots or patches under the skin.
Diagnosis and Treatment
Doctors usually diagnose Rocky Mountain spotted fever based on enough symptoms to indicate infection. Test results for RMSF can take a while to be sent to the doctor, so treatment often starts before the results are available.
RMSF is typically treated with oral or IV antibiotics, depending on the severity of the infection. Complications may require prolonged treatment.
If untreated, RMSF can lead to serious health problems, so it's important to call your doctor promptly if you notice any symptoms of RMSF, such as:
- high fever
- muscle aches
- red eyes
Without antibiotic treatment, RMSF can lead to health problems that involve the heart, lungs, and brain. In an extremely severe case, it can be fatal.
If your child is recovering from RMSF at home, follow the doctor's instructions for giving antibiotics. Allow your child to rest in bed until the fever and other symptoms are gone.
RMSF can be prevented by avoiding tick-infested areas, like woods and tall grasses, brush, shrubs, and low tree branches, and by taking precautions when spending time outdoors.
When they're playing outdoors, have kids wear light-colored clothing that makes ticks more visible and, if it's practical, long-sleeved shirts and long pants. Use an insect repellant that fends off ticks, being careful to follow the label instructions. Be sure to use a repellent that contains 10% to 30% concentration of DEET (look for N,N-diethyl-meta-toluamide).
Not all ticks carry the RMSF bacteria, but it's wise to remove any immediately. The longer a tick stays attached to the skin, the greater the chance of infection. It usually takes several hours for a tick to transmit the bacteria that cause RMSF once it has become attached to the skin.
To remove a dog tick, use tweezers to grasp it by the head (not just the body) as close to the skin as possible. Pull steadily until the tick dislodges. Without touching the tick, preserve it in a jar or plastic bag until you can show it to your doctor. Disinfect the bite area with alcohol, wash your hands, and call your doctor.
Since pets also can bring ticks into your home, check their skin and fur for ticks whenever they have been playing in tick-infested areas. Follow your veterinarian's advice about collars and other products that can be used to keep your pet tick-free.
If you have any concerns, talk with your doctor.
Reviewed by: Nicole A. Green, MD
Date reviewed: January 2014