Rocky Mountain Spotted Fever (tick-borne typhus fever)

Last Reviewed: July 2017

What is Rocky Mountain Spotted Fever?

Rocky Mountain spotted fever (RMSF) is a disease caused by the bite of a tick infected with the bacterium Rickettsia rickettsii. In New York, the American dog tick (Dermacentar variablis) is the most common tick that spreads the disease. Fewer than 50 cases are reported annually in New York State. RMSF is a serious illness that can be fatal in the first 8 days of symptoms if not treated correctly, even in previously healthy people. The course of the disease varies greatly. Patients who are treated early may recover quickly on outpatient medication, while those who experience a more severe course may require intravenous antibiotics, prolonged hospitalization or intensive care.

Who gets RMSF?

People of any age can get RMSF. In the eastern United States, children are infected most frequently, while in the western United States, adult males are more likely to become infected. Disease occurrence is directly related to exposure to tick-infested habitats or to infested pets.

How is RMSF spread?

RMSF is spread by the bite of an infected tick. In New York, the American dog tick (Dermacentar variablis) is the most common carrier. Person-to-person spread of RMSF does not occur.

What are the signs and symptoms of RMSF and when do they appear?

RMSF frequently begins with a sudden onset of moderate to high fever (which can last for 2 or 3 weeks), headache, abdominal pain, vomiting, and muscle pain. A rash may also develop, but is often absent in the first few days, and in some patients never develops. The rash is often present on the palms of the hands and soles of the feet and rapidly spread to the trunk or the rest of the body. Symptoms usually appear 2-14 days after the bite of an infected tick occurs.

How is RMSF diagnosed?

Symptoms and possible tick bite exposure may cause a health care provider to suspect RMSF. Laboratory testing can later confirm the diagnosis.

What is the treatment for RMSF?

A specific antibiotic called doxycycline is the first line of treatment for adults and children of all ages and should be started immediately when RMSF is suspected. It is most effective when this treatment is started within 5 days of when symptoms start. Since starting treatment early is crucial for survival of this disease, when RMSF is suspected, treatment should never be delayed while waiting for laboratory test results.

Does past infection with RMSF make a person immune?

One infection probably provides permanent immunity.

What can be done to prevent RMSF?

Generally, ticks cannot jump or fly onto a person. They wait in vegetation and cling to animals and humans when they brush by. Domestic animals can carry ticks into areas where you live such as your house or garage, so brush off animals and look for ticks before they enter these areas. The best prevention is through awareness. Check after every two to three hours of outdoor activity for ticks on clothing or skin. Brush off any ticks on clothing or skin before skin attachment occurs. A careful check of all body surfaces for attached ticks should be done at the end of the day. If removal of attached ticks occurs within 36 hours, the risk of tick-borne infection is minimal. For proper tick removal, please watch the video at Tick removal.

Insect repellents can be effective at reducing bites from ticks that can spread disease. If you decide to use a repellent, use only what and how much you need for your situation. More information on repellents can be found at Environmental Protection Agency - insect-repellents.

In addition:

  • Be sure to follow label directions.
  • Try to reduce the use of repellents by dressing in long sleeves and pants tucked into socks or boots.
  • Children should only handle repellents with adult supervision. Adults should apply repellents to their own hands first and then gently spread on the child's exposed skin. Avoid applying directly to children's hands. After returning indoors, wash your child's treated skin and clothing with soap and water or give the child a bath.
  • Do not apply near eyes, nose or mouth and use sparingly around ears.
  • After returning indoors, wash treated skin with soap and water.
  • Dogs are susceptible to RMSF and owners should use tick collars, sprays, shampoos, or medications regularly to protect their pets and families from ticks.

How should a tick be removed?

Grasp the mouthparts with tweezers as close as possible to the attachment (skin) site. Be careful not to squeeze, crush or puncture the body of the tick, which may contain infectious fluids. Pull firmly and steadily upward to remove the tick. After removing the tick, thoroughly disinfect the bite site and wash hands. The NYSDOH has created a video on proper tick removal (Proper Tick removal) and a printable card with steps on how to remove ticks (How to Remove a Tick Card). See or call a doctor if there are concerns about incomplete tick removal. Do not attempt to remove ticks by using petroleum jelly, lit cigarettes or other home remedies because these may actually increase the chance of contracting a tick-borne disease.