184.1 🎓 醫孞生版

184.1.0.1 📌 䞀頁重點

  • 菌: Borrelia spirochetes — distinct from Lyme group (Ch 185)
  • Two epidemiologic groups:
    • LBRF (Louse-Borne Relapsing Fever): Borrelia recurrentis — body louse (Pediculus humanus) — refugees, war, poverty, crowding; mortality 10-40% untreated; 2024 Ethiopia/Sudan/Ukraine outbreaks
    • TBRF (Tick-Borne Relapsing Fever): multiple Borrelia species (B. hermsii, B. turicatae, B. parkeri, B. duttonii, B. miyamotoi) — soft ticks (Ornithodoros); rodent reservoir; W USA caves/cabins, Africa, Asia
  • 臚床:
    • 突 high fever 2-7 d → spontaneous defervescence 4-14 d → relapse (1-10 cycles in TBRF, fewer in LBRF)
    • Fever cycles result from antigenic variation (Vmp surface proteins) escaping antibody
    • Headache, myalgia, hepatosplenomegaly, jaundice, rash, conjunctival injection
    • Complications: meningoencephalitis, myocarditis, ARDS, DIC, splenic rupture
  • Dx:
    • Peripheral blood smear during fever — spirochetes visible (Wright/Giemsa)! (Unique among bacterial infections — most bacteria not visible peripheral smear)
    • PCR, dark-field
    • Serology limited
  • Treatment:
    • Doxycycline 100 mg PO bid × 7-10d (preferred)
    • Erythromycin / azithromycin alt
    • Severe / meningoencephalitis: Ceftriaxone 2 g IV qd × 14d
    • Jarisch-Herxheimer reaction extremely severe — pre-medicate, ICU monitoring
  • B. miyamotoi — recently recognized; tick-borne (hard tick Ixodes scapularis); similar to Lyme range; similar treatment

184.1.0.2 1⃣ Microbiology

  • Borrelia — gram-neg-like spirochetes, helical
  • Cultivable on specialized media (BSK-II)
  • Antigenic variation: Vmp (variable major protein) — > 30+ variants per genome; each fever spike represents new variant
  • Immune escape causes relapsing pattern

184.1.0.3 2⃣ Louse-Borne Relapsing Fever (LBRF)

184.1.0.3.1 Vector
  • Pediculus humanus humanus (body louse — different from head louse)
  • 人 only host; person-to-person via crushing infected louse (released into skin abrasion)
  • NOT bite transmission — louse feces / crushed body
184.1.0.3.2 流行病孞
  • Crowding, poverty, refugees, war, prisons
  • Africa (Ethiopia, Sudan, Eritrea — 2024 ongoing)
  • Ukraine + Europe migrant routes (2022+)
  • Historical pandemics (Russia post-revolution 1920s, 5M cases, 500K deaths)
184.1.0.3.3 臚床
  • 高 mortality 10-40% untreated
  • Fewer relapses than TBRF (1-2 typical)
  • Severe: myocarditis, splenic rupture, hepatic failure, ARDS, DIC
184.1.0.3.4 Treatment
  • Single dose doxycycline 100-200 mg PO OR procaine PCN G 600,000 U IM
  • Pre-medicate for Jarisch-Herxheimer (acetaminophen, antipyretic, IV access)
  • ICU monitor 4-6 hr post-dose (severe Herxheimer with vasodilation, shock)
  • Delouse (clothing washing, hot water 60°C, permethrin)

184.1.0.4 3⃣ Tick-Borne Relapsing Fever (TBRF)

184.1.0.4.1 Vector
  • Ornithodoros soft ticks
  • Brief feeding (15-30 min, often at night while sleeping) — patients don’t remember bite
  • Rodent reservoirs (squirrels, mice)
  • Endemic regions: W USA (CA, AZ, CO, NM, OR, WA, ID, NV, UT), W Canada, Africa, S Europe, Middle East, China
184.1.0.4.2 Species + Location
  • B. hermsii — W USA cabins/caves (chipmunks, ground squirrels reservoir)
  • B. turicatae — TX, SW USA
  • B. parkeri — CA, OR
  • B. duttonii — E Africa (also LBRF-like)
  • B. miyamotoi — hard tick Ixodes (Lyme-area, USA NE/Midwest, Russia, Japan)
184.1.0.4.3 臚床
  • 倚次 relapses (5-10 typical) — longer course than LBRF
  • 鑑別 from malaria (cyclic fever)
  • Children + outdoor enthusiasts + cabin/cave visitors
184.1.0.4.4 Treatment
  • Doxycycline 100 mg PO bid × 7-10d
  • Erythromycin / azithromycin alt (pediatric)
  • Severe / CNS: ceftriaxone 2 g IV qd × 14d
  • Jarisch-Herxheimer also occurs (less severe than LBRF)

184.1.0.5 4⃣ B. miyamotoi

  • Recognized as human pathogen 2011
  • Ixodes scapularis (hard tick — same as Lyme)
  • USA NE/Midwest, also Russia, Japan
  • Sx: high fever, relapse less common (often single episode), headache, myalgia
  • May be confused with Lyme (same tick, different organism)
  • Dx: PCR (best), serology developing
  • Treatment: doxycycline (same as Lyme)
  • Co-infection with Borrelia burgdorferi possible

184.1.0.6 5⃣ 蚺斷

184.1.0.6.1 Peripheral Blood Smear
  • Spirochetes visible in plasma during fever spike
  • Wright / Giemsa / dark-field
  • Unique among bacterial infections (most bacteria require culture)
  • Sensitivity high during fever, low between
  • Repeat if first negative
184.1.0.6.2 PCR
  • Blood, CSF
  • Species-specific or pan-Borrelia
  • Useful when smear negative
184.1.0.6.3 Serology
  • Limited; cross-reacts with Lyme + syphilis
  • Confirmatory paired
184.1.0.6.4 Culture
  • BSK-II media, slow (1-2 wk), specialty labs
184.1.0.6.5 Lab
  • Anemia, thrombocytopenia
  • ↑ LFT, ↑ BUN/Cr
  • ESR/CRP ↑
  • DIC in severe

184.1.0.7 6⃣ Jarisch-Herxheimer in Relapsing Fever

  • 特別 severe in LBRF (50%+ cases)
  • Symptoms 1-3 hr post-antibiotic:
    • 高燒 → rigors
    • Tachycardia → hypotension/shock
    • Vasodilation → cytokine storm
    • Severe respiratory distress possible
  • TNF-α surge
  • ICU-level monitoring 4-6 hr
  • Pre-medicate: antipyretic, IV access ready
  • Anti-TNF Ab (pentoxifylline) — some advocacy