Eruptive rickettsioses

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    Last update: October 2022

     

     

    Rickettsioses are eruptive fevers caused by bacteria of the genus Rickettsia and transmitted to man by an arthropod vector. Three main groups are distinguished: typhus group, spotted fever group and scrub typhus group.

    Clinical features

    • Common to all forms:
      • Sudden onset of fever (temperature of over 39 °C) with severe headache and myalgias.
      • 3 to 5 days later; onset of generalised cutaneous eruption (see below).
      • Hypotension; non-dissociated rapid heart rate (variable).
      • Typhoid state: prostration, obnubilation, confusion and extreme asthenia, particularly marked in typhus forms.
      • Inoculation eschar: painless, black crusted lesion surrounded by a erythematous halo at the site of the bite. Always check for this significant sign.
      • Non-cutaneous signs vary from one form to another, and are atypical and variable (see below).

     

    Group Typhus Spotted fever Scrub typhus

    Form

    Epidemic typhus

    Murine typhus

    Mediterranean
    spotted fever

    Rocky Mountain spotted fever

    Other Old-World tick-borne fevers

    Scrub typhus

    Pathogen

    R. prowasekii

    R. typhi

    R. conorii

    R. rickettsii

    R. sibirica, R. australis

    O. tsutsugamushi

    Vector

    body lice

    rat fleas

    ticks

    ticks

    ticks

    mites

    Reservoir

    man

    rats

    dogs

    rodents

    rodents, dogs, etc.

    rodents

    Occurence

    epidemic

    endemic

    endemic

    endemic

    endemic

    sporadic

    Geographical distribution

    worldwide, conflicts; main sites: Burundi/Rwanda, Ethiopia

    worldwide

    around the mediterranean,
    Sub-Saharan Africa

    North America,
    Central America,
    Columbia, Brazil

    Southern Africa, Australia, Siberia

    Far East, India,
    South Pacific Area

    Rash

    maculopapular

    maculopapular

    maculopapular

    purpural

    maculopapular

    macular

    Eschar

    0

    0

    black necrotic area

    rare

    black necrotic area

    black necrotic area

    Typhoid state

    +++

    +++

    +/-

    +/-

    +/-

    +++

    Extra-cutaneous signs

    cough, myalgia, meningeal signs

    gastrointestinal signs

    meningeal signs

    gastrointestinal and neurological signs, hypotension

    variables

    meningeal signs

    Case fatality (%)

    30 (without treatment)

    5

    2

    5

    1

    0-30

     

    • Complications can be severe, and sometimes fatal: encephalitis, myocarditis, hepatitis, acute renal failure, haemorrhage etc.

    Laboratory

    Detection of specific IgM of each group by indirect immunofluorescence. The diagnosis is confirmed by 2 serological tests at an interval of 10 days. In practice, clinical signs and the epidemiological context are sufficient to suggest the diagnosis and start treatment.

    Treatment

    • Symptomatic treatment:
      • Hydration (PO or IV if the patient is unable to drink).
      • Fever: paracetamol PO (Chapter 1). Acetylsalicylic acid (aspirin) is contra-indicated due to the risk of haemorrhage.

     

    • Antibiotic a Citation a. Unlike borrelioses, antibiotic treatment of rickettsioses does not provoke a Jarisch-Herxheimer reaction. However, the geographical distribution of borrelioses and rickettsioses may overlap, and thus a reaction may occur due to a possible co-infection (see Borreliosis). for 5 to 7 days or until 3 days after the fever has disappeared:
      doxycycline PO

    Children under 45 kg: 2.2 mg/kg (max. 100 mg) 2 times daily

    Children 45 kg and over and adults: 100 mg 2 times daily

    In severe infections, a loading dose of doxycycline is recommended:

    Children under 45 kg: 4.4 mg/kg (max. 200 mg) on D1 then 2.2 mg /kg (max. 100 mg) 2 times daily

    Children 45 kg and over and adults: 200 mg on D1 then 100 mg 2 times daily

     

    • In a context of epidemic typhus, doxycycline PO is the choice treatment, but there is a risk of recurrence:
      Children: 4 mg/kg (max. 100 mg) single dose 
      Adults: 200 mg single dose

    Prevention

    • Epidemic typhus: control of body lice (see Pediculosis, Chapter 4).
    • Murine typhus: control of fleas and then rats.
    • Spotted fevers: avoid tick bites by wearing clothing and using repellents.
    • Scrub typhus: use of repellents, chemoprophylaxis with doxycycline PO (200 mg once weekly in adults).

     

    Footnotes
    • (a)Unlike borrelioses, antibiotic treatment of rickettsioses does not provoke a Jarisch-Herxheimer reaction. However, the geographical distribution of borrelioses and rickettsioses may overlap, and thus a reaction may occur due to a possible co-infection (see Borreliosis).