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Snapshot
  • A 35-year-old woman presents to a clinic in Australia for evaluation of fever, fatigue, and productive cough for 1 week. She had been doing a work-stay program on a sheep farm that specialized in exporting high-quality organic wool. On physical exam, she has rhonchi in the left lower lobe of the lung and chest radiography confirms the diagnosis of pneumonia. Given her occupational exposure, she is started on doxycycline.
Introduction
  • Classification
    • Coxiella burnetii
      • obligate intracellular gram-negative bacteria
      • Legionellales order
      • causes Q fever and culture-negative bacterial endocarditis
      • transmitted from farm animals (sheep, goat, and cattle amniotic fluid) via inhalation of aerosolized spores even at low doses
      • no arthropod vector
  • Epidemiology
    • incidence
      • found worldwide
    • risk factors
      • exposure to farm animals
      • occupational exposure to animal products (e.g., animal hides)
      • immunosuppression
  • Pathogenesis
    • C. burnetii is able to replicate in phagocytic vacuoles in low pH environments
    • can survive oxidative and osmotic stress
    • can survive in the environment for years
  • Prevention
    • Q fever vaccine is available in Australia for those with high occupational risk
  • Prognosis
    • may have prolonged course if untreated
    • most cases resolve with treatment
Presentation
  • Symptoms
    • fever and headaches
    • chronic infection
      • weight loss
      • night sweats
    • acute infection
      • pneumonia
        • cough
        • sore throat
  • Physical exam
    • acute infection
      • pneumonia
        • rhonchi on lung exam
        • shortness of breath
    • chronic infection
      • endocarditis
        • heart failure
        • shortness of breath
      • vascular infection
        • abdominal pain
        • infected aneurysm
        • vascular rupture
      • osteomyelitis
        • tenosynovitis
        • tenderness at site of infection
      • hepatitis
        • jaundice
Imaging
  • Chest radiography
    • indication
      • suspected pneumonia from acute Q fever
    • findings
      • lobar opacities or patchy infiltrates
  • Echocardiography
    • indication
      • suspected endocarditis from chronic Q fever
    • findings
      • vegetation on valves, most commonly mitral valve
Studies
  • Labs
    • blood cultures are usually negative
    • transaminitis
    • elevated erythrocyte sedimentation rate or C-reactive protein
    • confirmatory testing
      • detection of immunoglobulin G (IgG) on serology
      • detection of DNA on polymerase chain reaction
  • Making the diagnosis
    • based on clinical presentation and laboratory studies
    • suspect Q fever in cases of culture-negative endocarditis
Differential
  • Tularemia
    • distinguishing factor
      • typically presents with maculopapular rash that may ulcerate
  • Bacterial endocarditis
    • distinguishing factors
      • blood cultures are usually positive
      • other culture-negative endocarditis to consider are
        • Bartonella spp
        • HACEK (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella)
Treatment
  • Medical
    • doxycycline
      • indication
        • all patients
    • hydroxychloroquine
      • indication
        • chronic Q fever
        • given with doxycycline
    • trimethoprim/sulfamethoxazole
      • indication
        • for pregnant women
      • outcome
        • may reduce fetal death
Complications
  • Adverse fetal outcomes in pregnant women
 

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