Diseases & Conditions

Rocky Mountain spotted fever

Rocky Mountain spotted fever is a potentially serious bacterial infection transmitted to humans by tick bites. The illness is named after the Rocky Mountain region, where the disease was first identified. Rocky Mountain spotted fever occurs when an infected tick attaches to your skin and feeds on your blood. The infection then has the potential to spread to your bloodstream and other areas of your body.

Rocky Mountain spotted fever doesn't spread directly from person to person. If treated promptly, a case of Rocky Mountain spotted fever is usually fairly mild. In a small number of people, the disease can be serious, even fatal, especially in older adults. Because Rocky Mountain spotted fever can progress rapidly to a more widespread infection, prompt treatment is important.

Rocky Mountain spotted fever symptoms include:

• High fever — body temperature reaching 102 F (38.9 C) or greater
• Chills
• Severe headache
• Widespread aches and pains
• Restlessness
• Nausea and vomiting
• Loss of appetite
• Fatigue
• A rash of red spots or blotches

Two to 14 days after being bitten by an infected tick, you may develop nausea, headache, loss of appetite and a sore throat. As Rocky Mountain spotted fever develops, fever, chills, tenderness and soreness in your bones and muscles, restlessness, trouble sleeping (insomnia), abdominal pain and vomiting may occur. You may have a cough and, possibly, delirium, lethargy and stupor.

Between the third and fifth day of the fever, a red rash may appear on your wrists, ankles, palms of your hands and soles of your feet. The rash often spreads up your arms and legs to your torso.

A few people who are infected may not develop a rash (Rocky Mountain spotless fever). The absence of a rash does not indicate a milder form of illness, but makes the condition more difficult to diagnose.

The cause of Rocky Mountain spotted fever is the organism Rickettsia rickettsii. This bacterium most often is spread to humans by tick bites. Ticks can attach themselves to your skin and feed on your blood. They can lodge anywhere on your body, but often are found in your hair, around your ankles and in your genital area. Once embedded in your skin, ticks can cause a small, hard, itchy lump surrounded by a red ring or halo. The longer an infected tick stays attached to your skin, the greater your chance of acquiring infection.

Rocky Mountain spotted fever also can be transmitted through broken skin, such as a cut or scrape on your hands or fingers. Bacteria that cause this disease circulate in the fluids of a tick's body. If you squeeze or crush a tick as you remove it from yourself, another person or a pet, an infection can occur if the fluid comes in contact with an area of broken skin. It's also possible to develop an infection if you touch your eye after coming into contact with an infected tick.

The culprit ticks
The bacterium that causes Rocky Mountain spotted fever typically is carried by a family of ticks known as Ixodidaeor hard ticks. These ticks live in the low bushes and tall grasses of wooded areas and are more abundant in late spring and early summer.

In the western United States, Rocky Mountain spotted fever is transmitted by the wood tick (Dermacentor andersoni). In the eastern United States, where the disease is most common, it's transmitted by the American dog tick (Dermacentor variabilis). In the southern United States, Central America and South America, Rocky Mountain spotted fever is transmitted by other ticks, such as the lone star tick (Amblyomma americanum) and the brown dog tick (Rhipicephalus sanguineus).

Rocky Mountain spotted fever primarily occurs when ticks are most active and during warm weather when people tend to spend more time outdoors.

See your doctor if you develop a rash or become sick after a tick bite. Rocky Mountain spotted fever and other infectious diseases carried by ticks can progress rapidly and may be life-threatening. If possible, take the tick along with you to your doctor's office for laboratory testing.

Your doctor will likely be able to diagnose Rocky Mountain spotted fever by evaluating your signs and symptoms and by conducting a physical examination. In addition, he or she may order a blood test or examine a specimen of the rash or the tick itself to search for the presence of the organism that causes this infection.

If detected in its early stages, Rocky Mountain spotted fever can be most successfully treated with medication. Left untreated, the infection can spread from the site of the bite via your bloodstream, potentially causing infection in other areas of your body. Rocky Mountain spotted fever may cause serious complications involving your joints, heart, lungs, kidneys, and central and peripheral nervous system, such as:

• Heart, lung or kidney failure
• An infection of the membranes and fluid surrounding your brain and spinal cord (meningitis)
• Brain damage
• Problems with blood clotting
• Shock

In a small percentage of cases, Rocky Mountain spotted fever causes death, usually because treatment is delayed or is never sought.