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Key Features

Essentials of Diagnosis

  • Prodrome of headache, then chills and fever

  • Severe, intractable headaches, prostration, persisting high fever

  • Macular rash appearing on days 4–7 on the trunk and in the axillae, spreading to the rest of the body but sparing the face, palms, and soles

  • Diagnosis confirmed by complement fixation, microagglutination, or immunofluorescence

  • Disease may recrudesce (Brill-Zinsser disease)

General Considerations

  • Caused by Rickettsia prowazekii, an obligate parasite of the body louse Pediculus humanus corporis (other lice do not contribute)

  • Transmission is favored by crowded, unsanitary living conditions, famine, war, or any circumstances that predispose to heavy infestation with lice

  • After biting a person infected with R prowazekii, the louse becomes infected by the organism, which persists in the louse gut and is excreted in its feces

  • When the same louse bites an uninfected individual, the feces enter the bloodstream when the person scratches the itching wound

  • Dry, infectious louse feces may also enter via the respiratory tract

  • Because of aerosol transmissibility, R prowazekii is considered a possible bioterrorism agent

  • R prowazekii can survive in lymphoid and adipose tissues after primary infection, and years later, produce recrudescence of disease (Brill-Zinsser disease) without exposure to infected lice

Demographics

  • Cases can be acquired by travel to pockets of infection (eg, central and northeastern Africa, Central and South America)

  • Outbreaks have been reported from Peru, Burundi, and Russia

  • In the United States, cases occur among the homeless, refugees, and the unhygienic, most often in the winter.

Clinical Findings

Symptoms and Signs

  • Incubation period is 10–14 days

  • Prodromal symptoms

    • Malaise

    • Cough

    • Headache (may be severe)

    • Backache, arthralgia, myalgia

    • Chest pain

  • Prodromal symptoms are followed by

    • Abrupt onset of chills

    • High fever (can be prolonged)

    • Prostration, with flu-like symptoms progressing to delirium and stupor

  • Other findings

    • Conjunctivitis, mild vitritis, retinal lesions, optic neuritis

    • Hearing loss from neuropathy of the eighth cranial nerve

    • Abdominal pain

    • Splenomegaly

  • Flushed faces and macular rash (that may become confluent) appears first in the axillae and then over the trunk, spreading to the extremities on the fifth or sixth day of illness; sparing the palms of hands and soles of feet

  • In severely ill patients,

    • Rash becomes hemorrhagic, and hypotension becomes marked

    • Pneumonia, thromboses, vasculitis with major vessel obstruction and gangrene, circulatory collapse, myocarditis, uremia, seizure may occur

  • Improvement begins 13–16 days after onset with a rapid drop of fever and typically a spontaneous recovery

  • Compared to R prowazekii infection, Brill-Zinsser disease has

    • A more gradual onset

    • Shorter duration of fever and rash

    • A milder disease course

Differential Diagnosis

  • Typhoid fever

  • Meningococcemia

  • Measles

Diagnosis

Laboratory Findings

  • White blood cell count is variable

  • Thrombocytopenia, elevated liver enzymes, proteinuria, and hematuria commonly occur

  • In primary rickettsial infection, ...

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