MCQ of the Day: 22 October 2026

Answer: A. Larval trombiculid mite (chigger). The eschar in a concealed, moist site, fever after agricultural exposure in the post-monsoon season, thrombocytopenia and transaminitis are classic for scrub typhus, caused by Orientia tsutsugamushi. It is one of the commonest causes of acute undifferentiated febrile illness in India. Only the larval (chigger) stage of Leptotrombidium mites feeds on humans, and the organism passes transovarially, so the mite is both vector and reservoir. The IgM ELISA is the usual diagnostic test in India, while the Weil-Felix test (OX-K agglutination) is cheap but insensitive. Doxycycline or azithromycin is used for treatment.

B. The rat flea transmits Rickettsia typhi (murine typhus) and Yersinia pestis. Murine typhus seldom causes an eschar.

C. Hyalomma ticks transmit Crimean-Congo haemorrhagic fever virus. Indian tick typhus (R. conorii) is spread by Rhipicephalus ticks.

D. The body louse transmits R. prowazekii (epidemic typhus), Borrelia recurrentis and Bartonella quintana, usually in crowded, unhygienic conditions and without an eschar.