A forest worker in East Africa presents with repeated episodes of high fever followed by afebrile intervals of several days. Blood smear shows spirochaetes. He reports being bitten by small, painless bugs at night while sleeping in a mud hut with cracked earthen floors. Which vector is responsible?
- A Ixodes ricinus (hard tick)
- B Ornithodoros moubata (soft tick) ✓
- C Xenopsylla cheopis (rat flea)
- D Pediculus humanus corporis (body louse)
Correct answer: B. Ornithodoros moubata (soft tick)
Explanation
Tick-borne (endemic) relapsing fever due to Borrelia duttonii is transmitted by soft ticks of the genus Ornithodoros, which live in cracks of earthen floors and walls and take rapid, painless nocturnal blood meals. The relapsing pattern reflects antigenic variation of the spirochaete. Ixodes transmits Lyme disease and Russian spring summer encephalitis, the rat flea transmits plague, and the body louse causes louse-borne (epidemic) relapsing fever, a different Borrelia species transmitted in crowded, cold conditions.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.