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For further information, see CMDT Part 32-11: Typhus Group

Key Features

Essentials of Diagnosis

  • Exposure to mites in endemic South and East Asia, the western Pacific (including Korea), and Australia

  • Black eschar at site of the bite, with regional and generalized lymphadenopathy

  • High fever, relative bradycardia, headache, myalgia, and a short-lived macular rash

  • Frequent pneumonitis, encephalitis, and myocarditis

General Considerations

  • Caused by Orientia tsutsugamushi, which is a parasite of rodents and is transmitted by larval trombiculid mites (chiggers)

  • Disease is endemic in an area known as the "tsutsugamushi triangle" which is formed by

    • Korea

    • China

    • Taiwan

    • Japan

    • Pakistan

    • India

    • Thailand

    • Malaysia

    • Vietnam

    • Laos

    • Queensland, Australia

  • Cases are also reported in the Middle East, Kenya, and South America

  • Risk factors in China include

    • Female sex

    • Ages between 60 and 69 years

    • Farming

  • Transmission

    • Occurs more often at higher altitudes

    • Vertical transmission occurs

    • Blood transfusions may transmit the pathogen as well

Clinical Findings

Symptoms and Signs

  • Malaise, chills, severe headache and backache develop after a 1- to 3-week incubation period

  • At the site of the bite, a papule evolves into a flat black eschar (the groin and the abdomen being the most common sites followed by the chest and axilla)

  • Regional lymph nodes are commonly enlarged and tender, and sometimes a more generalized adenopathy occurs

  • Fever rises gradually during the first week of infection

  • Rash

    • Usually macular

    • Primarily on the trunk area

    • Can be fleeting or more severe, peaking at 8 days but lasting up to 21 days after onset of infection

  • Relative bradycardia

  • Gastrointestinal symptoms, including nausea, vomiting, and diarrhea, occur in nearly two-thirds of patients and correspond to the presence of

    • Superficial mucosal hemorrhage

    • Multiple erosions

    • Ulcers in the gastrointestinal tract

  • Acute kidney injury and other renal abnormalities are frequently present

Differential Diagnosis

  • Leptospirosis

  • Typhoid

  • Dengue

  • Malaria

  • Q fever

  • Hemorrhagic fevers

  • Tuberculous meningitis

  • Trigeminal neuralgia


  • Thrombocytopenia and elevation of liver enzymes, bilirubin, and creatinine are common

  • Indirect immunofluorescent assay (IFA) and indirect immunoperoxidase assays are

    • The gold standard for establishing the diagnosis

    • Expensive and have limited availability

  • An ELISA detecting Orientia specific antibodies in serum is available

  • PCR (from the eschar or blood)

    • Most sensitive diagnostic test

    • However, it remains positive even after initiation of treatment

  • Culture of the organism from blood obtained in the first few days of illness is another diagnostic modality but requires a specialized biological safety level 3 laboratory

  • Severe infections correlate with intermediate and high early IgG levels and higher levels of proteases, referred to as granzymes

  • Pulmonary disease outcome correlates with rapidity of fever clearance and the presence of anemia, facial puffiness, and maculopapular rash


  • Doxycycline (100 mg orally twice ...

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