Eruptive rickettsioses

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).

• 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).