188.1 🎓 醫孞生版

188.1.0.1 📌 䞀頁重點

  • 菌: Coxiella burnetii — small gram - obligate intracellular bacterium; highly resistant to environment (forms spore-like small-cell variant — survives years in dust)
  • Reservoir: 家畜 (cattle, sheep, goats — main); also cats, dogs, ticks, wild ruminants
  • Transmission:
    • Aerosol inhalation (#1 — even brief exposure, dust from contaminated farms, slaughterhouses, abattoir, wool, hides)
    • Unpasteurized dairy (uncommon)
    • Tick (rare in human)
    • NOT person-to-person
  • Highly infectious — 1 organism可臎感染 (bioterror Cat B)
  • 2 forms:
    • Acute Q fever (~ 60% asymptomatic, 40% sx):
      • Fever, severe headache, myalgia, pneumonia, hepatitis (“granulomatous donut” doughnut granuloma classic on liver biopsy)
      • Self-limited 2 wk usually
    • Chronic Q fever (~ 5% of acute, especially with predisposing valve/aneurysm):
      • Culture-negative endocarditis (#1 chronic form)
      • Vascular infection (mycotic aneurysm, vascular graft)
      • Chronic fatigue (Q-fever fatigue syndrome — QFS)
      • Osteo, hepatitis chronic
  • Risk for chronic: pre-existing valve disease, vascular graft / aneurysm, immunocompromise, pregnancy
  • Dx:
    • Serology IFA (Phase II Ab acute > Phase I; chronic = Phase I > Phase II — antigenic phase variation key for diagnosis)
    • PCR of blood / tissue
  • Treatment:
    • Acute: Doxycycline 100 mg PO bid × 14d
    • Chronic endocarditis / vascular: Doxycycline + Hydroxychloroquine ≥ 18 months (valve), ≥ 24 months (graft / aneurysm)
    • Pregnant + acute: TMP-SMX (avoid doxy)

188.1.0.2 1⃣ 现菌孞

  • Coxiella burnetii — obligate intracellular, small gram - rod
  • Forms spore-like small-cell variant (SCV) — extreme environmental resistance (years)
  • 2 antigenic phases:
    • Phase I (virulent form) — in nature, in chronic infection
    • Phase II (avirulent variant) — appears in lab culture, in acute infection
  • Phase variation used diagnostically
  • Bioterror Category B (highly infectious aerosol)

188.1.0.3 2⃣ 流行病孞

  • Global zoonosis; high in dairy/farming regions
  • High prevalence: France, Netherlands, Spain, Germany, Australia, USA western
  • Netherlands 2007-2010 outbreak: 4000+ human cases from goat farms (largest peacetime)
  • Occupational risk: farmer, veterinarian, abattoir worker, wool worker
  • Wind-borne: distant cases possible (km from source)
  • Most cases sporadic; outbreaks linked to specific farms

188.1.0.4 3⃣ Acute Q Fever

188.1.0.4.1 Clinical
  • 60% asymptomatic
  • 40% symptomatic:
    • Self-limited fever (high) + severe headache + myalgia
    • Atypical pneumonia (often mild, CXR with rounded opacities)
    • Hepatitis (transaminitis, often without jaundice; “doughnut” granuloma on liver biopsy classic — fibrin ring around central fat vacuole)
    • Rare: meningoencephalitis, pericarditis, myocarditis, rash
  • 2 wk duration typical, self-limited
188.1.0.4.2 Treatment
  • Doxycycline 100 mg PO bid × 14d — shortens duration, prevents chronic
  • Pregnancy: TMP-SMX 160/800 PO bid × until delivery (long course; prevents placental infection); doxy avoided

188.1.0.5 4⃣ Chronic Q Fever

188.1.0.5.1 Risk Factors
  • Pre-existing valve disease (greatest risk)
  • Vascular graft / aneurysm
  • Immunocompromise
  • Pregnancy (placental seeding)
  • ~ 5% of acute cases → chronic (higher with risk factors, up to 30% in valvular)
188.1.0.5.2 Forms
188.1.0.5.2.1 Endocarditis (#1)
  • Culture-negative endocarditis — classic
  • Pre-existing valve almost universal (rheumatic, prosthetic, bicuspid aortic)
  • Subacute presentation (months-years post-acute)
  • Constitutional + low-grade fever + heart failure + hepatosplenomegaly + clubbing
  • TEE: vegetation
  • High Phase I IgG titer (≥ 1:1024 or 800 depending lab)
188.1.0.5.2.2 Vascular Infection
  • Mycotic aortic aneurysm
  • Vascular graft infection
  • Tricky to detect — image abnormality + serology + PCR of tissue
188.1.0.5.2.3 Q-Fever Fatigue Syndrome (QFS)
  • Persistent fatigue + arthralgia + cognitive sx > 6 mo
  • ~ 20% of patients
  • Not necessarily active infection
  • Supportive + counseling; no benefit prolonged antibiotic
188.1.0.5.2.4 Other Chronic
  • Chronic hepatitis
  • Chronic pulmonary
  • Osteomyelitis
  • Genital infection (rare)
188.1.0.5.3 Treatment Chronic
  • Doxycycline 100 mg PO bid + Hydroxychloroquine 200 mg PO tid (combination)
  • HCQ alkalinizes phagosome → enhances doxy activity
  • Duration:
    • Endocarditis native: 18 months minimum (or normalization Phase I IgG)
    • Endocarditis prosthetic / vascular graft / aneurysm: 24 months minimum
  • Monitor Phase I IgG q3 mo, doxy/HCQ levels, drug toxicity (G6PD, retinal HCQ, photosensitivity)
  • Valve surgery as needed
188.1.0.5.4 Pregnancy Chronic
  • TMP-SMX during pregnancy → switch to doxy + HCQ postpartum
  • Long-term follow

188.1.0.6 5⃣ Diagnosis

188.1.0.6.1 Serology IFA (Indirect Fluorescent Antibody)
  • Phase I + Phase II IgM, IgG titers
  • Acute: Phase II > Phase I (Phase II IgG ≥ 1:200, IgM ≥ 1:50)
  • Chronic: Phase I > Phase II (Phase I IgG ≥ 1:800-1024 highly suggestive)
  • Paired sera if equivocal
188.1.0.6.2 PCR
  • Blood (acute), tissue (valve, aneurysm, abscess) — high sens chronic
  • Specialty / CDC labs
188.1.0.6.3 Other
  • Culture (BSL-3 only — bioterror)
  • Liver biopsy: “doughnut granuloma” (acute)
  • TEE: vegetation (chronic endocarditis)
  • PET-CT: vascular infection / vegetation

188.1.0.7 6⃣ Prevention

  • Avoid raw / unpasteurized dairy
  • Occupational PPE in high-risk farming
  • Q-Vax vaccine (Australia only — pre-employment screening for high-risk)
  • Outbreak: surveillance + animal management (vaccinate goats / sheep)