A79.8/A79.9
DESCRIPTION
Tick-borne infection due to Rickettsia conorii , acquired from dogs, or Rickettsia africae , acquired from cattle and game. The hallmark of tick bite fever is the eschar, i.e. round black lesion ± 5 mm in diameter with an inflammatory halo. A rash develops on about the third day of illness in about two thirds of patients with R. conorii and in fewer cases of R. africae infection. In R. conorii infection the rash is maculopapular and involves the palms and soles. In R. africae infection the rash is sparse and may be vesicular. The classic triad of fever, eschar and rash occurs in 50-75% of patients. Signs of severe tick bite fever include severe headache, hypotension, shortness of breath and neurological manifestations.
GENERAL MEASURES
- Application of insect repellent to exposed skin and clothing.
- Wearing long sleeves, long trousers and socks, if outside.
- Inspect clothing for presence of ticks after suspected exposure.
Complications include:
- vasculitis
- myocarditis
- encephalitis
- pneumonitis
- thrombosis
- thrombocytopaenia
- renal failure
MEDICINE TREATMENT
Antibiotic therapy:
Treatment must be started before confirmation of diagnosis by serology.
Although not recommended for children <8 years of age, doxycycline is still regarded as the medicine of choice for children with tick bite fever. However, due to the unavailability of lower dosage forms of doxycycline alternative medicines are considered in children <8years of age or those weighing <45kg with mild infection.
Mild to moderate infection:
Children< 45 kg
- Azithromycin, oral, 10 mg/kg/dose daily for 3 days. See paediatric dosing tool.
Children ≥ 45 kg and adults
- Doxycycline, oral, 100 mg 12 hourly, for at least 3 days after the fever subsides with clinical improvement.
- Maximum duration of treatment is 7 days.
In pregnancy:
- Azithromycin, oral, 500 mg 12 hourly for 3 days.
- In severe cases, initiate therapy with 1–2 days of doxycycline.
For headache and fever:
Children
- Paracetamol, oral, 15 mg/kg/dose, 6 hourly as required. See paediatric dosing tool.
Adults
- Paracetamol, oral, 1 g 4–6 hourly when required.
- Maximum dose: 15 mg/kg/dose.
- Maximum dose: 4 g in 24 hours
REFERRAL
- Patients unable to take oral therapy.
- Patients not responding to adequate therapy e.g. fever persisting for > 48 hours after initiation of treatment.
- Patients with complications.
- Patients with severe tick bite fever.