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Key Features

  • An acute, self-limiting, febrile illness

  • Caused by Rickettsia akari, a parasite of mice, transmitted by the mite Liponyssoides sanguineus

  • Infections are reported globally

  • Crowded conditions and mouse-infested housing allow transmission of the pathogen to humans

  • Has also been found in farming communities

Clinical Findings

  • Primary lesion is a painless red papule that vesiculates and forms a black eschar followed by an incubation period of 7–12 days

  • Onset of symptoms is sudden, with chills, fever, headache, photophobia, and disseminated aches and pains

  • Widespread papular eruption appears 2–4 days later

  • Rash becomes vesicular and forms crusts that are shed in about 10 days

  • Early lesions may resemble those of chickenpox (typically vesicular versus papulovesicular in rickettsialpox)

  • Pathologic findings include dermal edema, subepidermal vesicles, and a lymphocytic vasculitis

Diagnosis

  • Transient leukopenia and thrombocytopenia and acute hepatitis can occur

  • A fourfold rise in serum antibody titers to rickettsial antigen, detected by complement fixation or indirect fluorescent assays

  • Conjugated antirickettsial globulin can identify antigen in punch biopsies of skin lesions

  • Polymerase chain reaction (PCR) detection of rickettsial DNA in fresh tissue

  • R akari can also be isolated from eschar biopsy specimens

Treatment

  • Oral doxycycline (200 mg/day) for 7 days

  • Severe symptoms may require hospitalization

  • Control requires the elimination of mice from human habitations and insecticide applications

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