Murine typhus
Murine (endemic) typhus is a flea-borne rickettsial infection caused by Rickettsia typhi, found in tropical and subtropical areas and in Texas, California, and Hawaii, that presents with fever, headache, and a rash that starts on the trunk and spreads outward while sparing the palms and soles. Treat empirically with doxycycline 100 mg twice daily for 7 to 10 days on clinical suspicion, because serology often turns positive only in convalescence.
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What this article covers
- Overview
A flea-borne rickettsiosis: murine typhus, also called endemic typhus, is caused by Rickettsia typhi and transmitted by fleas.
- Epidemiology
Tropical and subtropical distribution: R typhi is prevalent in tropical and subtropical areas worldwide.
- Risk factors
Flea exposure, the defining exposure, since fleas are the vector of R typhi.
- Pathophysiology
Flea-borne inoculation: R typhi is transmitted to humans by fleas.
- Clinical features
Fever with headache and a truncal rash in a flea-exposed patient from an endemic area defines the presumptive clinical diagnosis: there is no formal criteria set; the combination of acute fever…
- Differential diagnosis
Rocky Mountain spotted fever: tick-borne (Dermacentor), most common in the South Atlantic states, with a rash that starts at the wrists and ankles and spreads to the trunk, palms, and soles; the most dangerous rickettsial mimic.
- Diagnosis
The diagnosis is confirmed by detecting R typhi during the acute stage, before antibiotics: polymerase chain reaction (PCR), immunohistochemical analysis of tissue, or culture during acute illness…
- Management
First, start doxycycline 100 mg PO or IV twice daily on clinical suspicion, without waiting for confirmation: continue for 7 to 10 days and until the patient has been afebrile for at least 48 hours.
- Complications
Shock: the most life-threatening result of rickettsial microvascular injury.
- Prognosis
Prompt doxycycline is the main determinant of outcome: empiric therapy on clinical suspicion prevents progression to shock, meningoencephalitis, and organ damage.
- Prevention
Avoid flea exposure in tropical and subtropical areas and in endemic parts of Texas, California, and Hawaii, since fleas are the vector.
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