What is the recommended treatment for scrub typhus?

Treatment of Scrub Typhus

Doxycycline is the drug of choice for scrub typhus in all patients, including children under 8 years, and should be started immediately when the disease is suspected without waiting for laboratory confirmation. 1

First-Line Treatment Regimen

Adults

• Administer doxycycline 100 mg twice daily (oral or IV) for at least 3 days after fever resolves and until clinical improvement is evident 1
• The minimum treatment duration is 5-7 days 1
• Severe or complicated disease may require longer courses 1

Children

• For children weighing less than 45 kg, give doxycycline 2.2 mg/kg body weight twice daily (oral or IV) 1
• The historical concern about dental staining in children under 8 years should not prevent short-course doxycycline use 1
• Treatment duration follows the same principles as adults: at least 3 days after fever subsides with a minimum 5-7 day course 1

Critical Treatment Principles

Timing is Essential

• Treatment must never be delayed while awaiting laboratory confirmation, as delay can lead to severe disease, long-term sequelae, or death 1
• Patients typically respond within 24-48 hours of appropriate antibiotic therapy 1
• Lack of response within 24-48 hours should prompt consideration of alternative diagnoses 1

Expected Clinical Response

• Fever clearance typically occurs within 21-29 hours of treatment initiation 2
• The disease causes vasculitis through endothelial cell infection, which responds rapidly to appropriate antibiotics 1
• Mortality rates up to 4% have been reported in untreated or delayed treatment cases 1

Alternative Treatment Options

Azithromycin

• A single 500 mg dose of azithromycin is as effective as a 1-week course of doxycycline for mild scrub typhus 2
• This is the recommended alternative for pregnant women and children when doxycycline concerns exist 3, 4
• Cure rates of 100% have been demonstrated with single-dose azithromycin in mild disease 2

Rifampin

• Rifampin 600 mg once daily for 5 days shows equivalent efficacy to doxycycline 5
• This is particularly important in areas with documented doxycycline resistance (parts of northern Thailand) 5, 4
• Rifampin remains effective against doxycycline-resistant strains 5

Important Clinical Caveats

Resistance Considerations

• While doxycycline resistance has been documented in parts of northern Thailand, it remains rare in most endemic areas 4
• In regions with known resistance, rifampin should be considered as first-line therapy 5, 4

Diagnostic Pitfalls

• Do not rely on a single serologic test to confirm or exclude diagnosis 6
• The characteristic eschar (painless necrotic lesion with black crust) is not always present 1
• Early antibiotic therapy can diminish or delay antibody development 6

Treatment Monitoring

• Continue treatment for at least 3 days after fever subsides regardless of when clinical improvement begins 1
• Never stop treatment prematurely even if the patient appears clinically well 1