Scrub typhus management

1. Uncomplicated disease

2. Severe or complicated scrub typhus

• Give IV doxycycline plus IV azithromycin in severe disease, then step down to oral therapy when appropriate.
• A multicenter randomized trial found combination IV doxycycline plus azithromycin superior to either alone in severe scrub typhus (Varghese et al., NEJM 2023, PMID 36856615).
• Provide organ support as indicated:
  • Oxygen, noninvasive or invasive ventilation for pneumonitis/ARDS
  • Careful IV fluids and vasopressors for shock
  • Renal monitoring and dialysis if required
  • Management of seizures/encephalitis, myocarditis, hepatic dysfunction, and co-infections

3. Alternatives and cautions

• Azithromycin: preferred in pregnancy and a useful alternative for doxycycline intolerance or suspected poor response.
• Rifampicin: can be effective in selected uncomplicated cases or locations with reduced doxycycline response, but avoid using it if tuberculosis is possible or untreated, because it may partially treat TB and promote resistance.
• Chloramphenicol: an alternative, but less favored because of toxicity and reports of nonresponse/relapse.
• Avoid beta-lactams such as penicillins and cephalosporins as sole therapy. They do not reliably treat Orientia tsutsugamushi.

4. Investigations and monitoring

• CBC with platelet count
• Liver enzymes, bilirubin, creatinine, electrolytes
• Urinalysis and urine output
• Chest radiograph if respiratory symptoms
• ECG/troponin/echocardiography if cardiac symptoms
• Tests for malaria, dengue, leptospirosis, enteric fever, and other locally relevant infections
• IgM ELISA/IFA and PCR where available. PCR from an eschar can be more useful than blood PCR.

5. Prevention

Latest guidance for severe scrub typhus

Recommended approach

1. Treat immediately when suspected
   • Do not wait for confirmatory IgM, IFA, or PCR in a patient with compatible febrile illness and organ dysfunction in an endemic setting.
   • Send diagnostic specimens before antibiotics if this does not delay therapy. Eschar PCR, when an eschar is present, can be useful.
2. Admit to HDU/ICU Severe disease includes at least one organ-system complication, for example:
   • Hypoxemic pneumonia or ARDS
   • Shock or myocarditis
   • Acute kidney injury
   • Encephalitis, meningitis, seizures, or altered mental state
   • Significant hepatitis/liver failure
   • Bleeding, DIC, or multiorgan dysfunction
   The CDC clinical overview similarly lists MODS, hemorrhage, ARDS, encephalitis, pneumonia, renal or liver failure, and death as severe manifestations.
3. Antibiotics: use IV doxycycline plus IV azithromycin for severe disease
   • The pivotal evidence is the INTREST multicenter, double-blind RCT in 794 patients aged 15 years or older with severe scrub typhus and at least one organ involvement.
   • Combination IV doxycycline plus azithromycin for 7 days reduced the composite endpoint of death, persistent complications at day 7, or persistent fever at day 5:
     • 33% with combination treatment
     • 47% with doxycycline alone
     • 48% with azithromycin alone
   This was statistically superior to either monotherapy, while 28-day mortality and adverse events were similar between groups. See Varghese et al. NEJM trial abstract (2023, PMID: 36856615).
   Harrison's 2025 edition reflects this direction: “In severe scrub typhus, the combination of doxycycline and azithromycin is beneficial compared to monotherapy.”
4. Provide standard critical-care support
   • Oxygen, lung-protective ventilation and ARDS management when needed
   • Judicious fluids, vasopressors for shock, and echocardiography if myocarditis/cardiac dysfunction is suspected
   • Close monitoring of urine output, creatinine, liver tests, CBC/platelets, coagulation parameters, lactate, and respiratory status
   • Renal replacement therapy for indicated severe AKI
   • Management of seizures/encephalitis, DIC, secondary bacterial infection, and relevant co-infections according to usual ICU protocols
5. Pregnancy and doxycycline allergy
   • These cases require infectious-disease and obstetric input.
   • CDC retains doxycycline as first-line treatment for suspected scrub typhus in all age groups, but advises specialist-directed treatment in pregnancy. Azithromycin or rifampin may be considered for severe doxycycline allergy. CDC treatment guidance
   • Evidence for the dual-IV regimen is from patients aged 15 years or above, so do not automatically extrapolate it to younger children or pregnancy.

Important nuance about “latest guidelines”

• The CDC page, updated May 2024, still gives broad scrub typhus treatment advice: doxycycline is the treatment of choice, continued until clinical improvement and for at least 3 days after defervescence. It does not publish a separate ICU combination-antibiotic protocol.
• A 2025 standard operating protocol by Pannu reports severity-stratified care and recommends dual therapy in severe, confirmed cases, but its full dosing protocol should be checked through the original publication and reconciled with local antimicrobial policy.
• Therefore, the strongest current practical recommendation for adult/adolescent severe disease is: early ICU-level care plus 7 days of IV doxycycline and IV azithromycin, guided by local dosing standards, renal/hepatic status, oral absorption, and drug availability.