What is the recommended treatment for scrub typhus?

Scrub Typhus Treatment

Doxycycline is the drug of choice for treating scrub typhus in all patients, including children under 8 years of age, and should be initiated immediately when scrub typhus is suspected based on clinical presentation—never delay treatment while awaiting laboratory confirmation. 1, 2

First-Line Treatment Regimen

Adults

• 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

Children

• Under 45 kg: Doxycycline 2.2 mg/kg body weight twice daily (oral or intravenous) 1, 2
• 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 of Administration Decision Algorithm

• Intravenous therapy: Use for hospitalized patients who are vomiting, obtunded, or severely ill 2
• Oral therapy: Acceptable for early disease managed outpatient or stable inpatients 2

Expected Clinical Response

• Fever typically subsides within 24-48 hours after initiating doxycycline when treatment starts during the first 4-5 days of illness 1, 2
• Lack of response within 48 hours should prompt consideration of alternative diagnoses 1, 2
• Early treatment reduces complications and mortality significantly 3

Alternative Agents

When Doxycycline Cannot Be Used

• Azithromycin: Single 500 mg dose has shown equivalent efficacy to 7-day doxycycline course in mild scrub typhus 4
• Chloramphenicol: 12.5-25 mg/kg every 6 hours IV (maximum 1 g/dose) 1
• Rifampin: 600 mg once daily for 5 days shows equivalent efficacy to doxycycline 5

Pregnancy and Young Children

• Azithromycin is recommended for pregnant women and children when doxycycline concerns exist 6
• However, the historical concern about dental staining in children under 8 years should not prevent short-course doxycycline use, as limited tetracycline exposure has negligible effect on permanent tooth color 1, 2

Critical Clinical Considerations

Timing Is Everything

• Treatment must be initiated immediately based on clinical suspicion 1, 2
• Delay in treatment can lead to severe disease, long-term sequelae, or death 1, 2
• Patients who received early anti-scrub antibiotics had fewer complications and no mortality compared to those treated late 3

Geographic Considerations

• Doxycycline resistance has been documented in parts of northern Thailand 6
• Rifampin is effective in areas where doxycycline resistance is present 6
• In most endemic areas without documented resistance, doxycycline remains highly effective 5

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, 2
• For liquid formulations: multiply total mg dose by 0.2 if using 25 mg/5 mL suspension, or by 0.1 if using 50 mg/5 mL suspension 1

Premature Discontinuation

• Do not discontinue treatment prematurely—continue for at least 3 days after fever resolution 1, 2
• Ensure minimum 5-7 day total course is completed 1, 2
• Single-dose regimens (e.g., 200 mg doxycycline) have shown efficacy in some studies 7, but current guidelines recommend longer courses for optimal outcomes 1, 2

Delayed Diagnosis

• Include doxycycline or azithromycin in initial empirical antimicrobial therapy for febrile patients during tick season in endemic areas 3
• Look for characteristic eschar (painless necrotic lesion with black crust at bite site), though not always present 1
• Fever beginning 6-10 days after potential chigger exposure with headache, myalgia, and malaise should raise suspicion 1