This is another spotted fever virus like Rocky Mountain spotted fever (RMSF). It is spread by Dermacentor occidentalis (Pacific Coast tick) in California. The primary symptom is fever, but a headache, muscle ache, and fatigue are also seen. Instead of a rash, Eschars are found where the tick bites, similar to Rickettsia parkeri. Antibody tests may cross-react with Rickettsia rickettsii. The CDC recommends as a precaution that all patients should be treated as if they have RMSF.
Specific diagnosis can be made from a swab or biopsy of the eschar by PCR, immunohistochemistry tissue stains, or cell culture.