Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF) is a bacterial disease caused by Rickettsia rickettsii, which is transmitted to humans through the bite of an infected tick. The disease is characterized by a distinctive rash, fever, and headache.

Cause and Transmission

RMSF is caused by the bacterium Rickettsia rickettsii, which is found in the United States and parts of Central and South America. The primary vectors of transmission are the American dog tick (Dermacentor variabilis), the Rocky Mountain wood tick (Dermacentor andersoni), and the brown dog tick (Rhipicephalus sanguineus). Ticks become infected with R. rickettsii when they feed on infected animals, such as rodents and dogs.

Symptoms

The symptoms of RMSF typically begin within 2-14 days after the tick bite and may include:

• Fever
• Headache
• Rash, which usually appears 2-5 days after the onset of fever
• Nausea and vomiting
• Abdominal pain
• Muscle pain
• Joint pain

Diagnosis

RMSF is diagnosed based on a combination of clinical presentation, laboratory tests, and epidemiological information. Laboratory tests may include:

• Indirect immunofluorescence assay (IFA)
• Enzyme-linked immunosorbent assay (ELISA)
• Polymerase chain reaction (PCR)

Treatment

The treatment of choice for RMSF is doxycycline, which should be started as soon as possible after diagnosis. The recommended dosage is 100 mg every 12 hours for adults and children over 8 years old, and 2.2 mg/kg every 12 hours for children under 8 years old.

Prevention

Prevention of RMSF involves avoiding tick bites and removing attached ticks promptly. Measures to prevent tick bites include:

• Using insect repellents, such as DEET or picaridin
• Wearing protective clothing, such as long-sleeved shirts and pants
• Avoiding wooded and bushy areas where ticks are common
• Conducting regular tick checks on the body

Complications

If left untreated, RMSF can lead to serious complications, including:

• Meningitis
• Encephalitis
• Pneumonia
• Septic shock
• Death

Prognosis

The prognosis for RMSF is generally good if treatment is started promptly. However, if left untreated, the disease can be fatal in up to 20% of cases.