(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 
.)
Epidemic typhus is a rickettsial disease.
Humans are the natural reservoir for R. prowazekii, which is prevalent worldwide and transmitted by body lice when louse feces are scratched or rubbed into bite or other wounds (or sometimes the mucous membranes of the eyes or mouth). In the US, humans occasionally contract epidemic typhus after contact with flying squirrels.
Fatalities are rare in children < 10 years, but mortality increases with age and may reach 60% in untreated patients > 50 years.
Symptoms and Signs of Epidemic Typhus
After an incubation period of 7 to 14 days, fever, headache, and prostration suddenly occur. Temperature reaches 40° C in several days and remains high, with slight morning remission, for about 2 weeks. Headache is generalized and intense. Small, pink macules, which appear on the 4th to 6th day, rapidly cover the body, usually in the axillae and on the upper trunk and not on the palms, soles, and face. Later, the rash becomes dark and maculopapular. In severe cases, the rash becomes petechial and hemorrhagic.
Splenomegaly sometimes occurs. Hypotension occurs in most seriously ill patients. Vascular collapse, renal insufficiency, encephalitic signs, ecchymosis with gangrene, and pneumonia are poor prognostic signs.
Brill-Zinsser disease, a mild recrudescence of epidemic typhus, can occur years after the initial infection if host defenses falter.
Diagnosis of Epidemic Typhus
Clinical features
Biopsy of rash with fluorescent antibody staining to detect organisms
Acute and convalescent serologic testing (serologic testing not useful acutely)
Polymerase chain reaction (PCR)
Louse infestation is usually obvious and strongly suggests typhus if history (eg, living in or visiting an endemic area) suggests possible exposure.
Treatment of Epidemic Typhus
Doxycycline
Primary treatment of epidemic typhus is doxycycline 200 mg orally once followed by 100 mg twice a day in adults until the patient improves, has been afebrile for 24 to 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.
Severely ill patients with epidemic typhus may have a marked increase in capillary permeability in later stages; thus, IV fluids should be given cautiously to maintain blood pressure while avoiding worsening pulmonary and cerebral edema.
Prevention of Epidemic Typhus
Immunization and louse control are highly effective for prevention. However, vaccines are no longer available. Lice may be eliminated by dusting infested people with malathion or lindane.
Key Points
Epidemic typhus is prevalent worldwide; humans are the natural reservoir.
Infection is transmitted among humans by body lice when louse feces are scratched or rubbed into louse bites, wounds, or mucous membranes.
Small, pink macules rapidly cover the body, later, becoming dark and maculopapular.
Mortality increases with age and may reach 60% in untreated patients > 50 years; vascular collapse, renal insufficiency, encephalitic signs, ecchymosis with gangrene, and pneumonia are poor prognostic signs.
Suspect epidemic typhus based on clinical manifestations and signs of louse infestation; confirm with fluorescent antibody staining of skin biopsy.
Treat with doxycycline or chloramphenicol.
Brill-Zinsser disease, a mild recrudescence of epidemic typhus, can occur years after the initial infection if host defenses falter.
Brill-Zinsser Disease
Patients with Brill-Zinsser disease acquired epidemic typhus earlier or lived in an endemic area. Apparently, when host defenses falter, viable organisms retained in the body are activated, causing recurrent typhus; thus, disease is sporadic, occurring at any season or geographic area, and in the absence of infected lice. Lice that feed on patients may acquire and transmit the agent.
Symptoms and signs of Brill-Zinsser disease are almost always mild and resemble those of epidemic typhus, with similar circulatory disturbances and hepatic, renal, and central nervous system changes. The remittent febrile course lasts about 7 to 10 days. The rash is often evanescent or absent. Mortality is nil.
See the Overview of Rickettsial and Related Infections for diagnosis Diagnosis 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 and treatment Treatment 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 details.
Drugs Mentioned In This Article
| Drug Name | Select Trade |
|---|---|
doxycycline |
VIBRAMYCIN |
chloramphenicol |
No US brand name |
ciprofloxacin |
CILOXAN, CIPRO |
lindane |
No US brand names |
permethrin |
ELIMITE, NIX |
