Treatment of Scrub Typhus
Doxycycline is the first-line treatment for scrub typhus in all patients, including children under 8 years and pregnant women, and should be initiated immediately based on clinical suspicion without waiting for laboratory confirmation. 1, 2
First-Line Treatment: Doxycycline
Adult Dosing
- Doxycycline 100 mg twice daily (oral or intravenous) 1, 2
- Continue for at least 3 days after fever subsides with evidence of clinical improvement 1, 2
- Minimum total treatment course: 5-7 days 1, 2
Pediatric Dosing
- Children under 45 kg: Doxycycline 2.2 mg/kg body weight twice daily (oral or intravenous) 1, 2
- Children 45 kg or greater: Use adult dosing (100 mg twice daily) 1, 2
- Loading dose option: 4.4 mg/kg as single dose, then 2.2 mg/kg every 12 hours 1
Route Selection
- Intravenous therapy: Use for hospitalized patients who are vomiting, obtunded, or have severe disease 2
- Oral therapy: Acceptable for early disease managed outpatient or stable inpatients 2
Critical Clinical Considerations
Timing of Treatment
- Treatment must be initiated immediately when scrub typhus is suspected based on clinical presentation 1, 2
- Never delay treatment while awaiting laboratory confirmation, as delay can lead to severe disease, long-term sequelae, or death 1, 2
- Patients typically respond within 24-48 hours after initiating doxycycline when treatment is started during the first 4-5 days of illness 2, 3
- Lack of response within 48 hours should prompt consideration of alternative diagnoses 1, 2
Use in Special Populations
- Children under 8 years: The historical concern about dental staining should NOT prevent use of doxycycline for short courses of treatment 1, 2
- Limited use of tetracyclines during the first 6-7 years of life has negligible effect on permanent tooth color 2
- Short-term courses (≤21 days) of doxycycline show no evidence of dental staining or enamel hypoplasia 1
Alternative Treatment Options
Azithromycin
- Effective alternative with comparable treatment success rates to doxycycline 4, 5
- Single 500 mg dose has been shown effective for mild scrub typhus 6
- Preferred in pregnancy and children when doxycycline is contraindicated 7
- May have longer time to defervescence (approximately 4 hours longer) compared to doxycycline 5
- Lower frequency of adverse effects compared to doxycycline 5
Chloramphenicol
- Dose: 12.5-25 mg/kg every 6 hours intravenously 1
- Can be used as alternative agent when doxycycline is not suitable 1
- Historically effective but less commonly used due to safety concerns 7, 4
Other Antibiotics
- Rifampicin: Has been studied but should not be first-line due to risk of inducing resistance in undiagnosed tuberculosis 4
- Tetracycline: Effective but doxycycline preferred due to better dosing schedule 4
Expected Clinical Response
- Fever resolution: Typically within 24-48 hours of appropriate antibiotic therapy 1, 2, 3
- Median time to defervescence: 21-29 hours with doxycycline 6
- Early treatment (before day 9 of illness) associated with fewer and milder complications 3
- Treatment failure rates are low across all effective antibiotics 4
Common Pitfalls to Avoid
Dosing Errors
- Always calculate dose based on actual body weight, not age alone 1, 2
- Verify syrup concentration before calculating mL doses to avoid underdosing 1
- For 25 mg/5 mL suspension: multiply total mg dose by 0.2 to get mL volume 1
- For 50 mg/5 mL suspension: multiply total mg dose by 0.1 to get mL volume 1
Treatment Duration
- Do not discontinue prematurely: Continue for at least 3 days after fever resolution 1, 2
- Ensure minimum 5-7 day total course is completed 1, 2
- Severe or complicated disease may require longer treatment courses 1
Diagnostic Delays
- Do not wait for laboratory confirmation before initiating treatment 1, 2
- Patients who received prior anti-scrub treatment had fewer complications and no deaths compared to those treated late 3
- Average duration of illness before presentation in fatal cases was 9.2 days 3