Scrub typhus — DTM&H MCQ

Correct answer: B — Scrub typhus

The correct answer is B, scrub typhus. This trekker from rural Nepal has the classic triad of fever, a painless eschar with regional lymphadenopathy, and laboratory findings of thrombocytopenia with mildly deranged liver enzymes, which together point to infection with Orientia tsutsugamushi transmitted by trombiculid mite (chigger) bites in rural, scrub or forested terrain across Asia including Nepal. The eschar marks the mite bite site and is a highly specific clue that is frequently missed on cursory examination, often found in skin folds such as the groin or axilla. Dry cough reflects the interstitial pneumonitis that can accompany rickettsial infection. Doxycycline should be started empirically once scrub typhus is suspected clinically, without waiting for serological confirmation, because delayed treatment risks progression to multi-organ failure. Why the other options are wrong: E. Enteric fever: Salmonella Typhi causes fever, relative bradycardia and abdominal symptoms but does not produce an eschar or localised tender lymphadenopathy at a bite site. A. Leishmaniasis: Cutaneous or visceral leishmaniasis presents with chronic ulcerating skin lesions or hepatosplenomegaly and pancytopenia over weeks to months, not an acute eschar with tender regional nodes after a short trek. C. Cutaneous anthrax: This produces a painless black eschar too, but arises from contact with infected animals or animal products, not mite exposure in rural terrain, and typically lacks the systemic thrombocytopenia and transaminitis seen here. D. Dengue fever: Dengue causes fever and thrombocytopenia but there is no eschar or mite-bite lymphadenopathy, and the rash pattern and headache profile differ from rickettsial disease. Key point: An eschar plus tender regional lymphadenopathy in a returning traveller from rural Asia is pathognomonic for scrub typhus and mandates empirical doxycycline without awaiting serology.

Reference: Journal of Infection (British Infection Association) - Case report, 'From eschar to diagnosis: scrub typhus causing multi-organ failure in a returning traveller', 2025, https://www.sciencedirect.com/science/article/pii/S1470211825000259