++
For further information, see CMDT Part 34-12: Typhus Group
++
Rickettsia typhi, a ubiquitous pathogen recognized on all continents, is transmitted from rat to rat through the rat flea
Humans usually acquire the infection in an urban or suburban setting when bitten by an infected flea
Endemic typhus is usually self-limited
Rare human cases in the developed world occur in travelers, usually to Southeast Asia (significant underdiagnosis has been documented in Indonesia), Africa, or the Mediterranean area, although other pockets of infection are also known to occur in the Andes and the Yucatán
In the United States, cases are reported along the Gulf Coast
Sun exposure appears to correlate with increased exposure risk
++
Fever, headache, myalgia, and chills
Relative bradycardia is reported
Maculopapular rash occurs in around 50% of cases; it is concentrated on the trunk, mostly sparing the palms and soles, and fades rapidly
Untreated infections last an average of 12–15 days
Rare presentations include pain or painful genital (Lipschutz) ulcers
Anemia, thrombocytopenia, leukopenia, hyponatremia, and elevated levels of liver enzymes commonly occur
If illness is acquired during early pregnancy, it may be associated with transaminitis and may have a favorable prognosis
Murine typhus acquired early in pregnancy may be associated with
Miscarriage
Preterm birth
Low birth weight
Maternal death
Differential diagnosis: Rocky Mountain spotted fever, COVID-19 (which is also associated with a multisystem inflammatory syndrome)
Complications
Pneumonia (most common), pleural effusion, and respiratory failure
Neurologic (peripheral facial paralysis, meningitis, ataxia, seizures)
Acute kidney injury, focal segmental glomerulosclerosis
Fulminant myocarditis
Multiorgan failure
Ocular findings, disseminated intravascular coagulation, and hemophagocytic lymphohistiocytosis syndrome are rare
++
Serologic confirmation may be necessary for differentiation, with complement-fixing or immunofluorescent antibodies detectable within 15 days after onset, with specific R typhi antigens
A fourfold rise in serum antibody titers between the acute and the convalescent phase is diagnostic, although cutoff values for diagnosis are not standardized
R typhi antigens frequently cross-react with those of R prowazekii; polymerase chain reaction (PCR) can distinguish between these two infections (depending on the sample type, the timing of sample collection, bacterial load, and severity of disease)
During the first week of illness, PCR is the most sensitive test if samples are taken before doxycycline administration
++
Doxycycline
Dosage: 100 mg orally twice daily for 3 days (or until the patient is afebrile for 48 hours)
Drug of choice, except during pregnancy
Ciprofloxacin (500–750 mg orally twice daily) and ampicillin (500 mg orally three times daily) are reportedly successful in pregnant women
Azithromycin is frequently used but is not associated with improved fetal outcomes
Prognosis with treatment is excellent
Preventative measures are directed at control of rats and ectoparasites (rat fleas) with insecticides, rat poisons, and rat-proofing of buildings