Disease Fact Sheet Series:

What is Rocky Mountain spotted fever?

Rocky Mountain spotted fever (RMSF) is a disease caused by a microorganism transmitted to humans by the bite of an infected American dog tick (Dermacentor variabilis) and by several other tick species. Only 15 cases were reported in Wisconsin between 1980 and 2000. Most of these infections were acquired outside of Wisconsin.

Who gets RMSF?

RMSF is rare in Wisconsin. The majority of cases in the U.S. occur in the southeastern states. In spite of its name, the disease is not common in the mountain states. Children and young adults are most frequently affected. Disease incidence is directly related to exposure to tick infested habitats.

How is RMSF spread?

RMSF is spread by the bite of an infected tick (the American dog tick, the lone-star tick or the wood tick) or by contamination of the skin with the tick's body fluids or feces. Person to person and direct animal to human transmission of RMSF does not occur.

What are the symptoms of RMSF?

RMSF is characterized by a sudden onset of moderate to high fever (which can last for two or three weeks), severe headache, fatigue, deep muscle pain, chills and rash. The rash begins on the legs or arms, may include the soles of the feet or palms of the hands and may spread rapidly to the trunk or rest of the body. Not every case of RMSF will have the rash.

How soon do symptoms appear?

Symptoms usually appear between 3 to 14 days after the bite of an infected tick.

Does past infection with RMSF make a person immune?

One attack probably provides permanent immunity.

What is the treatment for RMSF?

Certain antibiotics such as tetracycline or chloramphenicol are used to treat the disease.

What can be done to prevent the spread of RMSF?

Frequent checking of one's clothing and skin for ticks when in infested areas is extremely useful in reducing disease. Tick repellents applied to legs and clothing may be helpful to prevent tick attachment. Mowing grass frequently in yards and along fences helps to reduce tick populations.

How should a tick be removed?

To remove an attached tick, grasp it with tweezers or forceps as close as possible to its attachment (skin) site, and pull straight back and out with a firm and steady pressure. If tweezers are not available, use fingers shielded with tissue paper or rubber gloves. Do not handle with bare hands. Be careful not to squeeze, crush or puncture the body of the tick which may contain infectious fluids. After removing the tick, thoroughly disinfect the bite site and wash hands. See or call a physician if there is concern about incomplete tick removal. It is important that a tick be removed as soon as it is discovered. Check for ticks frequently after being in tick infested areas. If tick removal occurs within three hours after attachment, the risk of tick-borne infection is reduced.

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Last Revised: September 03, 2009