(See also Overview of Rickettsial and Related Infections Overview of Rickettsial and Related Infections Rickettsial diseases (rickettsioses) and related diseases (anaplasmosis, ehrlichiosis, Q fever, scrub typhus) are caused by a group of gram-negative, obligately intracellular coccobacilli. All... read more .)
Murine typhus is a rickettsial disease.
Animal reservoirs include cats, wild opossums, rats, mice, and other rodents. Rat fleas and probably cat fleas and opossum fleas transmit organisms to humans through bites. Fleas are also natural reservoirs for R. typhi; infected female fleas can transmit organisms to their progeny. Distribution is sporadic but worldwide; the incidence is low but higher in rat-infested areas.
After an incubation of 6 to 18 days (mean 10 days), a shaking chill accompanies headache and fever in patients with murine typhus. The fever lasts about 12 days; then temperature gradually returns to normal.
The rash and other manifestations are similar to those of epidemic typhus but are much less severe. The early rash is sparse and discrete.
Mortality is low but is higher in older patients.
Primary treatment is doxycycline 200 mg orally once followed by 100 mg twice a day in adults until the patient improves, has been afebrile for 48 hours, and has received treatment for at least 7 days. Chloramphenicol 500 mg orally or IV 4 times a day for 7 days is 2nd-line treatment. Oral chloramphenicol is not available in the US, and its use is associated with adverse hematologic effects, which requires monitoring of blood indices.
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