What is the recommended treatment for scrub typhus?

Scrub Typhus Diagnosis and Treatment

Doxycycline is the treatment of choice for scrub typhus in all age groups, including children, with a recommended adult dose of 100 mg every 12 hours for 5-7 days or until 48-72 hours after the patient becomes afebrile. 1

Diagnosis

Clinical Presentation

• Incubation period: 6-21 days after mite bite
• Initial symptoms:
  • Sudden onset of fever
  • Severe headache
  • General malaise
  • Myalgias
• Characteristic findings:
  • Eschar (present in only ~33% of patients)
  • Maculopapular rash (appears 2-4 days after fever onset, may become petechial)
  • Neurological manifestations (18% of patients)
  • Acute respiratory distress syndrome (9% of patients)

Diagnostic Tests

• Early disease (<7 days): Quantitative PCR is most sensitive
• Later disease: IgM ELISA and rapid diagnostic tests show excellent sensitivity and specificity
• Serology: Indirect immunofluorescence (IFI) is the reference test for detecting IgM and IgG
• Immunohistochemistry: For detecting rickettsiae in skin biopsies

Treatment Recommendations

First-Line Treatment

• Doxycycline:
  • Adults: 100 mg every 12 hours orally or intravenously 1, 2
  • Children <45 kg: 2.2 mg/kg every 12 hours (maximum 100 mg per dose) 1
  • Duration: 5-7 days or until 48-72 hours after the patient is afebrile 1

Alternative Treatment

• Azithromycin:
  • Recommended for pregnant women and those who cannot take doxycycline 1
  • Single 500-mg dose has been shown to be as effective as a 1-week course of doxycycline for mild scrub typhus 3
  • May have longer time to defervescence compared to doxycycline (median 21 hours vs. 29 hours) 3
  • Lower frequency of adverse effects compared to other anti-rickettsial drugs 4

Other Alternatives

• Rifampin:

  • 600 mg once daily for 5 days
  • Equivalent treatment effects and safety compared to doxycycline 5
  • May be considered for areas with doxycycline-resistant strains 5

• Minocycline:

  • Effective for mild scrub typhus
  • May have faster defervescence than azithromycin in some regions 6

Treatment Considerations

Timing of Treatment

• Early treatment is critical:
  • Initiate treatment within the first 5 days of illness to significantly reduce mortality 1
  • Do not delay treatment pending laboratory confirmation or rash development 1
  • Patients who receive early anti-rickettsial treatment have fewer and milder complications 7

Special Populations

• Pregnant women: Azithromycin is the preferred treatment 1
• Children <8 years: Doxycycline remains the treatment of choice despite traditional concerns about dental staining, as the risk-benefit ratio favors its use in serious rickettsial infections 1
• Severe disease: Consider combination therapy or longer treatment duration

Prevention

• Avoid mite-infested areas
• Use protective clothing (long sleeves, long pants)
• Apply DEET-containing repellents
• Use permethrin-treated clothing
• Regular ectoparasite control for pets

Prognosis

• Good prognosis with early diagnosis and appropriate treatment
• Mortality increases with delayed treatment
• Approximately 4% mortality in untreated cases due to multiorgan dysfunction

Common Pitfalls to Avoid

• Delayed treatment: Do not wait for laboratory confirmation before starting treatment
• Inadequate treatment duration: Continue treatment until 48-72 hours after defervescence
• Misdiagnosis: Consider scrub typhus in patients with unexplained fever, especially in endemic areas
• Inappropriate antibiotic choice: Avoid using antibiotics not effective against rickettsial diseases