A shepherd sleeping in mud huts on a hill pasture develops repeated febrile episodes separated by afebrile intervals of about a week. Blood smear shows spirochaetes. No lice are found, but soft ticks are abundant in cracks of the hut walls. The vector and organism are:

• A Ornithodoros species and Borrelia duttoni ✓
• B Pediculus humanus corporis and Borrelia recurrentis
• C Rhipicephalus species and Rickettsia conorii
• D Xenopsylla cheopis and Yersinia pestis

Explanation

Tick-borne endemic relapsing fever is transmitted by soft ticks of the genus Ornithodoros, with Borrelia duttoni as the classic agent; infection can pass transovarially to tick progeny, maintaining the parasite in the hut walls for years. Louse-borne epidemic relapsing fever involves Borrelia recurrentis and occurs in crowded, famine settings without tick exposure.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.