Rocky Mountain Spotted Fever

RocAy Mountain Spotted Fever is a disease caused by the bacterium Rickettsia rickettsia, when it infects a person through the bite of an infected tick. Despite its name, this disease is not limited to the Rocky Mountain area.


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Rlckettsial diseases

Tick-borne diseases

Ken Takes a Hike

One June day, Ken took his dogs and hiked up to the top of Bitternut Mountain. The next morning when he was taking a shower, he found a tick attached to his neck at the hairline. He got his dad to remove the tick.

About 10 days later, seemingly out of nowhere, Ken developed a fever of more than 102 degrees Fahrenheit. His muscles ached, and he complained of having the worst headache of his life. Two days later, Ken's ankles and wrists were covered with a spotted rash. By the next day, the rash had spread to his whole body. Ken's parents took him to the emergency room, and he was given antibiotics to take for the next seven days. Gradually his fever, rash, and headache disappeared. Ken had had Rocky Mountain Spotted Fever.

What Are Rickettsial Diseases?

Rickettsial diseases are caused by a group of bacteria called Rickettsia. Lice, fleas, ticks, and mites can carry Rickettsia in their bodies, and can infect humans and other animals by biting them and injecting the bacteria into the bloodstream. Typhus, Q fever, trench fever, and the spotted fevers are all rickettsial diseases.

Rocky Mountain spotted fever (RMSF) is the best known of the rickettsial diseases. It occurs when a person is bitten by a tick (American dog tick, wood tick, or lone-star tick, depending on the geographic location) infected with Rickettsia rickettsia.

Ticks are eight-legged animals related to spiders and mites that live on the blood ot humans and other animals. A person also can get RMSF when liquid from a crushed tick gets into a cut or scrape, so it is important never to squeeze ticks with bare fingers.

What Happens When People Get RMSF?

The classic symptoms of RMSF are a history of tick bite, fever, head-ache, and a rash. However, symptoms of RMSF vary greatly from person to person; some people never get a rash, others do not get headaches, and only about 70 percent of people know a tick has bitten them.

In addition to the physical symptoms, doctors suspect RMSF and begin drug treatment if it is the right season and the right geographic location for ticks, and if the person was outdoors in areas where ticks live. Blood tests are done to confirm RMSF, but results can take days to weeks.

Wood ticks carrying Rickettsia rickettsia are vectors for Rocky Mountain Spotted Fever. © S.J. Krasemann/Peter Arnold, Inc.
Wood ticks carrying Rickettsia rickettsia are vectors for Rocky Mountain Spotted Fever.
© S.J. Krasemann/Peter Arnold, Inc.

Today, only 3 to 5 percent of people with RMSF die, but in the 1950s, 13 to 25 percent died. Diagnosing the disease quickly and starting treatment with antibiotics is the key to surviving RMSF.

How Can RMSF Be Prevented?

Although avoiding places where ticks live during tick season (woods and fields) might prevent RMSF, this is not practical for many people. A person venturing into such places should wear protective clothing, such as long sleeves and pants with tight-fitting wrists and ankles, and should use tick-repellent chemicals.

It takes about six hours after a tick attaches to the skin before it passes Rickettsia into a person's bloodstream, so people should check their bodies for ticks promptly after they have been outdoors in areas where ticks are found.

Ticks should be removed using tweezers or fingers covered with paper, not bare fingers. The tick is grabbed as close as possible to the skin and pulled out. The area is then washed with soap and water. Camping stores also sell special devices for extracting ticks without crushing or touching them.

The U.S. and the World

  • About 800 people per year are diagnosed with Rocky Mountain spotted fever in the United States.
  • Children aged 5 to 9 are most frequently infected, followed by men over age 60. RMSF is most common in white males.
  • Approximately 90 percent of cases occur between April and September, because ticks become active in warm weather.
  • The first case of RMSF was described in the Snake River Valley of Idaho in 1899, but the name comes from cases later reported throughout the Rocky Mountains.
  • RMSF can be found throughout North, Central, and South America.
  • RMSF occurs mostly in the south-eastern and south central United States.

See also
Bacterial Infections
Lyme Disease


The U.S. National Center for Infectious Diseases (NCIDOD) is part of the Centers for Disease Control and Prevention (CDC). It posts information about Rocky Mountain Spotted Fever at its website.

Also read article about Rocky Mountain Spotted Fever from Wikipedia

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