Rocky Mountain spotted fever

Causative Agent

Rickettsia rickettsii, Rickettsia parkeri & Rickettsia philipii

Type of Organism

Rickettsia Bacterial Species

Length of Attachment for Transmission

6 Hours

Initial Symptoms

• Symptoms may begin 2-12 days after exposure
• Non-specific symptoms such as headache, fever, nausea, vomiting may be occur first followed by a rapid progression into more severe and life threatening illnesses.
• A spotted rash varying in presentation will occur in a majority of patients.
• If left untreated, amputation may be necessary due to blood vessel damage.
• In severe cases, mental and physical disability may occur.

Diagnosis and Testing

• Skin biopsies may be tested using an immunostaining technique to confirm the presence of Rickettsial species.
• When testing for antibodies specific to Rickettsial species, Indirect Immunofluorescence Assays (IFA) are performed on two samples.
• The first sample is collected within 7 days of infection and will be compared to the second sample collected 2-4 weeks after infection.
• When testing for antibodies specific to Rickettsial species, Indirect Immunofluorescence Assays (IFA) are performed on two samples.
• Rickettsial species will be diagnosed if the second sample shows the number of antibodies present has increased since the first sample was tested.
• A false negative is possible in the first 7-10 days of illness and will commonly occur when the first sample is tested.
• Blood test results of low platelet count, low sodium levels, or elevated liver enzyme levels can assist with diagnosis.

CDC Treatment Recommendation

• Adults: Doxycycline 100mg-2x daily for 5-7 days.
• Children: 2.2mg/kg-2x daily for 5-7 days.

If antibiotic treatment is not provided within the first few days of infection, significant mortality rates of 20-30% are seen.

Disease Pathogenesis

Rickettsial species will infect cells that line blood vessels causing vascular inflammation known as Rickettsial vasculitis.