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Rocky Mountain Spotted Fever

American Dog Tick

What is Rocky Mountain spotted fever?

  • Rocky Mountain spotted fever (RMSF) is a bacterial disease caused by the bacterium, Rickettsia rickettsii.  
  • RMSF is one of the deadliest tickborne diseases in the U.S.
  • RMSF is transmitted by ticks, most commonly the American dog tick (Dermacentor variabilis).  
  • The American dog tick is the most common tick in Michigan, human cases of RMSF are rare but do occur.  
  • Rocky Mountain spotted fever can be fatal if treatment is not started within the first 5 days of illness.  
  • Physicians in Michigan who suspect RMSF should begin treatment with doxycycline immediately and not wait for results of laboratory testing.
  • Preventing tick bites is the best way to avoid getting RMSF.
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