A 25-year-old man from rural Assam presents with fever for 10 days, an eschar on the axilla, and generalised macular rash. Weil-Felix reaction is OXK positive (titre 1:320), OX2 and OX19 negative. What is the most likely diagnosis and first-line treatment?
- A Indian tick typhus (Rickettsia conorii); doxycycline
- B Scrub typhus (Orientia tsutsugamushi); doxycycline ✓
- C Epidemic typhus (Rickettsia prowazekii); doxycycline
- D Q fever (Coxiella burnetii); doxycycline
Explanation
Scrub typhus caused by Orientia tsutsugamushi is transmitted by larval trombiculid mites (chiggers) and is endemic in the Himalayan foothills, NE India, and tash-gan (OXK positive areas). The Weil-Felix reaction in scrub typhus shows agglutination of Proteus OXK strain only (OX2 and OX19 are negative), differentiating it from epidemic typhus (OX19 positive) and spotted fever group (OX2 and OX19 positive). The characteristic eschar (tache noire) at the mite bite site and macular rash are hallmarks. Doxycycline 100 mg BD for 7 days is first-line; azithromycin is used in pregnancy and children.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.