🐭 Rodents are the main reservoir globally, except in East Africa where humans themselves act as the reservoir. 🦟 Transmitted by soft ticks (Ornithodoros spp.), which feed quickly and often unnoticed at night.

🧾 About

Caused by Borrelia duttonii and related spirochetes.
Endemic in parts of Africa, Asia, and the Americas.
Transmission occurs when infected ticks feed → spirochetes in saliva enter bloodstream.
Unlike louse-borne relapsing fever, multiple relapses are common due to Borrelia’s antigenic variation.

🩺 Clinical Features

Incubation: 5–15 days.
Fever: recurrent high fevers lasting 3–10 days, separated by afebrile periods of 5–7 days.
Headache, meningitis-like symptoms, rigors, myalgia, arthralgia.
Hepatosplenomegaly and jaundice may develop.
Thrombocytopenia → petechiae, epistaxis, serosal haemorrhage.
Relapses may occur 3–10 times if untreated.
Severe cases: myocarditis, pneumonia, neurological involvement (meningoencephalitis).

🔬 Investigations

Microscopy: Spirochetes seen on peripheral blood smear (best during febrile episode) or dark-field microscopy.
FBC: Anaemia, thrombocytopenia, leukopenia.
Serology/PCR: can confirm diagnosis where available.

💊 Management

Adults: Tetracycline 500 mg PO QID for 7–10 days.
Children & Pregnancy: Erythromycin 500 mg PO QID for 7–10 days.
Alternative: Doxycycline 100 mg PO BD for 7–10 days.
Jarisch–Herxheimer reaction ⚠️: common after first dose → fever, rigors, hypotension → supportive management (fluids, antipyretics, monitoring).
Supportive care: fluids, analgesia, monitoring for complications.

📊 Comparison: Louse-Borne vs Tick-Borne Relapsing Fever

Feature	🪳 Louse-Borne (B. recurrentis)	🦟 Tick-Borne (B. duttonii & others)
Reservoir	Humans only 👤	Rodents 🐭 (except East Africa: humans)
Vector	Body louse (Pediculus humanus)	Soft tick (Ornithodoros spp.)
Transmission	Via crushed louse → inoculation into skin	Via tick saliva during feeding
Geography	Africa (Ethiopia, Sudan), refugee/war settings 🌍	Africa, Asia, Americas (endemic rural areas)
Incubation	5–15 days	5–15 days
Relapses	Usually 1–2 relapses 🔁	Multiple relapses (up to 10)
Severity	Often more severe; higher mortality ⚠️	Usually milder but prolonged
Complications	Myocarditis, meningoencephalitis, jaundice	Hepatosplenomegaly, CNS involvement, bleeding
Treatment	Tetracycline, Doxycycline, or Penicillin	Tetracycline or Doxycycline; Erythromycin if pregnant/children
Jarisch–Herxheimer Reaction	Very common (up to 80%) ⚡	Also occurs but less frequent
Prevention	Delousing, improved hygiene 🚿	Vector control, housing improvement, rodent control 🛡️

🛡️ Prevention

Vector control: avoid tick-infested areas, improve housing conditions.
Bed nets, insect repellents, and avoidance of rodent habitats.
Public health measures important in endemic regions.

📚 References

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Tick-borne relapsing fever (Borrelia duttonii)