Rocky Mountain Spotted Fever (RMSF)

Rocky Mountain spotted fever (RMSF)

Although RMSF is considered rare in Minnesota, MDH receives a few reports every year in patients with no travel history. A Dakota County child who contracted the infection in Minnesota died of RMSF in 2009.
RMSF is carried by Dermacentor ticks, which are common in wooded or brushy areas throughout the state.

  • Signs of RMSF can include fever, maculopapular or petechial rash, and thrombocytopenia.
  • To prevent severe disease, tetracycline treatment should be initiated for any suspect cases while test results are pending, even for children.
Full May 6, 2011: Tick-borne Disease Health Alert


Rocky Mountain spotted fever (RMSF) is rare in Minnesota, but isolated cases have been reported from various parts of the state. The disease is more common in the eastern, southern and western states. The illness is caused by bacteria called Rickettsia rickettsii, which is transmitted locally by the tick species Dermacentor variabilis (American dog tick, also called the wood tick). American dog ticks are found in grassy or wooded areas throughout Minnesota. They are most active from spring thru mid-summer.

Signs and Symptoms

Signs and symptoms include an abrupt onset of fever, malaise, headache, myalgias, loss of appetite, nausea, and vomiting, and a rash. The typical rash first appears as spots on the wrists and ankles which then spread to the trunk and also sometimes the palms and soles. The rash often appears two to five days after onset of fever. RMSF can result in organ failure and death.

Supportive laboratory findings include thrombocytopenia, increased serum hepatic aminotransferase levels, and hyponatremia.


The illness is treated with tetracycline in adults and children. Treatment should be undertaken with the assistance of an infectious disease specialist. Empiric treatment should be initiated as soon as RMSF is suspected to prevent serious complications or death.



  • Reporting Rocky Mountain Spotted Fever
    Minnesota Rules Governing Communicable Diseases require health care providers to report confirmed or suspected cases of Rocky Mountain spotted fever to the Minnesota Department of Health (MDH) within 1 working day.

MDH staff also are available to provide clinical consultation regarding diagnosis and treatment of Rocky Mountain spotted fever and other tick-borne diseases. Call 651-201-5414 for a clinical consultation.


Updated Thursday, May 05, 2011 at 03:33PM