Background
- Causes murine typhus, flea-borne typhus, or endemic typhus
Microbiology
- Flea-borne Gram-negative intracellular bacterium
Life Cycle
- Flea bites, flea poops, feces get rubbed into the bite wound
- Flea acquires infection from feeding on a rickettsemic host
Epidemiology
- Flea vector (Xenopsylla cheopis) with a rat reservoirs (Rattus)
- Also, cat flea vector (Ctenocephalides felis) in southern US
- Possibly opossums as reservoirs
- Worldwide distribution
- In the US, most cases are in southern Texas and California
Clinical Manifestations
- Incubation period of 1 to 2 weeks, but rarely remember flea exposure
- Fever, headache, nausea and vomiting are common, as well as myalgias
- Rash develops over the course in about 50%
- Usually described as macular or maculopapular rash, sometimes with petechiae
- On trunk, but can involve extremities
- Rarely on palms and soles
- May have leukopenia and thrombocytopenia early in the course
- Elevated AST is common, as well as other liver enzymes
- Further nausea/vomiting and anorexia, cough, and hepatosplenomegaly may all develop
- Neurologic complications include confusion, seizures, and ataxia
- They often develop hypoalbuminemia and electrolyte abnormalities such as hyponatremia and hypocalcemia
- CSF shows aseptic meningitis
- 1 to 4% mortality
- Sort of like a milder version of Rickettsia prowazekii
Diagnosis
- Based on acute and convalescent serology looking for a 4-fold risk after about 4 weeks
- Possibly PCR of skin biopsy
Management
- doxycycline 100 mg PO bid for 7 to 10 days
- Should be treated empirically, since cannot confirm diagnosis quickly
