Rocky Mountain spotted fever (RMSF) is an infection caused by the bacterium Rickettsia rickettsia. The illness is contracted from the bite of an infected tick, most commonly the American dog tick or the Rocky Mountain wood tick. The Centers for Disease Control and Prevention (CDC) reports RMSF is uncommon, with an attack rate of 2.2 cases yearly for every million people in the U.S. Although rare, RMSF is not to be taken lightly as the illness can be fatal. Antibiotics are the mainstay of treatment to rid the body of the causative bacteria. Other medications are used as needed to control the systemic effects of the disease.
Doxycycline
The CDC recommends the antibiotic doxycycline as the drug of choice for children and adults who have or are suspected of having RMSF. Unlike some other infections wherein antibiotics are not started until there is laboratory confirmation of the diagnosis, antibiotic therapy is begun immediately when there is a strong suspicion of RMSF. A treatment delay increases the risk of severe disease, which may result in death.
The CDC-recommended dose of doxycycline is 100 milligrams every 12 hours for adults, and 2.2 milligrams per kilogram of body weight every 12 hours for children who weigh less than 100 pounds. Doxycycline treatment continues at these doses for at least three days after the fever breaks. The CDC recommends a minimum of 5 to 10 days of antibiotic treatment. People with severe disease may require a longer course of antibiotic therapy.
Chloramphenicol
Doxycycline is usually not the drug of choice for pregnant women with RMSF because the drug may cause tooth and bone malformations in the unborn child. The alternative antibiotic is chloramphenicol. Like doxycycline, this antibiotic is effective against the RMSF bacterium. Chloramphenicol carries a warning required by the Food and Drug Administration because of a risk of bone marrow toxicity. With this adverse effect, the bone marrow fails to produce sufficient blood cells. The drug must be stopped if this side effect occurs.
Chloramphenicol may also cause a potentially fatal side effect--grey baby syndrome--in newborn babies of mothers who took chloramphenicol shortly before delivery. Grey baby syndrome symptoms include abdominal distention, shock and breathing distress. Death may occur within hours.
Anticonvulsants and Vasopressors
RMSF can affect the brain, causing seizures. The treatment team will employ anticonvulsant drugs to control seizure activity in these situations. Vasopressors--drugs that boost blood pressure--are used to restore a viable blood pressure if shock develops. Other drugs are used as required, depending on the specific manifestations of the RMSF infection.
References
- Centers for Disease Control and Prevention: Rocky Mountain Spotted Fever Treatment
- Centers for Disease Control and Prevention, MMWR: Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever, Ehrlichioses, and Anaplasmosis --- United States
- Mayo Clinic: Rocky Mountain Spotted Fever, Treatments and Drugs
- Merck Manual: Rocky Mountain Spotted Fever Treatment
- Centers for Disease Control and Prevention: Rocky Mountain Spotted Fever Natural History
