A 30-year-old software engineer from Himachal Pradesh presents with fever for 10 days, eschar on the right ankle, generalised maculopapular rash, and severe headache. Weil-Felix test shows OX-K agglutinin titre 1:320, OX-2 negative, OX-19 negative. PCR for Orientia tsutsugamushi is positive. Regarding treatment, which is TRUE?

• A Chloramphenicol is preferred over doxycycline for scrub typhus as it achieves better CNS penetration
• B Co-trimoxazole provides adequate coverage and is used where doxycycline is unavailable
• C Doxycycline 100 mg BD for 7–14 days is the first-line treatment; azithromycin is used in pregnancy and children under 8 years ✓
• D Scrub typhus is self-limiting; antibiotic therapy is reserved for severe disease with ARDS or multiorgan dysfunction

Explanation

The Weil-Felix OX-K positivity (Proteus OX-K agglutination) with OX-2 and OX-19 negative is characteristic of scrub typhus (Orientia tsutsugamushi), confirmed here by PCR. Doxycycline 100 mg BD for 7–14 days is the drug of choice and typically produces dramatic clinical improvement within 24–48 hours. In pregnancy and children <8 years (where tetracyclines are contraindicated), azithromycin 500 mg/day for 3–5 days is the alternative and shows comparable efficacy. Chloramphenicol was historically used but is not currently preferred. Co-trimoxazole is NOT active against Orientia. Scrub typhus can be fatal if untreated — early antibiotic therapy is mandatory.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.