Rocky mountain spotted fever

Other Names: RMSF Rocky Mountain spotted fever refers to an infection caused by the bacterium Rickettsia rickettsia. This particular bacterium is carried by certain species of ticks and spread to humans through the bites of infected ticks. Most people who get sick with RMSF will have a fever, headache, and rash. RMSF can be deadly if not treated early with the right antibiotic.

Transmission

Rocky Mountain spotted fever is a serious tickborne illness which can be deadly if not treated early.

Epidemiology

There are between 500 and 2500 cases of Rocky Mountain spotted fever reported in the United States per year,and in only about 20% can the tick be found. It is spread by several species of ticks in the United States, including the American dog tick (Dermacentor variabilis) pdf icon, Rocky Mountain wood tick (Dermacentor andersoni) pdf icon, and, in parts of the southwestern United States and Mexico, the brown dog tick (Rhipicephalus sanguineus) pdf icon. RMSF cases occur throughout the United States, but are most commonly reported from North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma.

Signs and Symptoms

Early signs and symptoms are not specific to RMSF (including fever and headache). However, the disease can rapidly progress to a serious and life-threatening illness. See your healthcare provider if you become ill after having been bitten by a tick or having been in the woods or in areas with high brush where ticks commonly live.

Signs and symptoms can include:

• Fever
• Headache
• Rash
• Nausea
• Vomiting
• Stomach pain
• Muscle pain
• Lack of appetite
• Rash

Rash is a common sign in people who are sick with RMSF. Rash usually develops 2-4 days after fever begins. The look of the rash can vary widely over the course of illness. Some rashes can look like red splotches and some look like pinpoint dots. While almost all patients with RMSF will develop a rash, it often does not appear early in illness, which can make RMSF difficult to diagnose.

Long-term Health Problems RMSF does not result in chronic or persistent infections. Some patients who recover from severe RMSF may be left with permanent damage, including amputation of arms, legs, fingers, or toes (from damage to blood vessels in these areas); hearing loss; paralysis; or mental disability. Any permanent damage is caused by the acute illness and does not result from a chronic infection.

Diagnosis

Even doctors who are familiar with the disease find it hard to diagnose early during infection.

Abnormal laboratory findings seen in patients with Rocky Mountain spotted fever may include a low platelet count, low blood sodium concentration, or elevated liver enzyme levels. Serology testing and skin biopsy are considered to be the best methods of diagnosis. Although immunofluorescent antibody assays are considered some of the best serology tests available, most antibodies that fight against R. rickettsii are undetectable on serology tests the first seven days after infection.

Differential diagnosis includes dengue, leptospirosis, chikungunya, and Zika fever.

Treatment

RMSF can be life-threatening. Early treatment with the antibiotic doxycycline can prevent death and severe illness. Doxycycline is the recommended antibiotic treatment for RMSF in adults and children of all ages.

Prevention

• There is no vaccine to prevent RMSF. Prevent illness by preventing tick bites, preventing ticks on your pets, and preventing ticks in your yard.
• Ticks live in grassy, brushy, or wooded areas, or even on animals, so spending time outside camping, gardening, or hunting will bring you in close contact with ticks.

Before You Go Outdoors

• Treat clothing and gear with products containing permethrin. Permethrin can be used to treat boots, clothing and camping gear and remain protective through several washings.
• Use Environmental Protection Agency (EPA)-registered insect repellentsexternal icon containing DEET, picaridin, IR3535, Oil of Lemon Eucalyptus, or 2-undecanone.
• Do not use products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) on children under 3 years old.

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