Updated: 12/27/2021

Coxiella

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  • Snapshot
    • A 50-year-old man presents to the emergency room for prolonged fever, shortness of breath, and chest pain. He is admitted for heart failure and suspected endocarditis. A cardiac echocardiogram shows vegetation on the valves. The initial blood cultures are negative. Upon further investigation, he works at a leather supplier and often visits farms to evaluate the cattle. He is treated for a suspected zoonotic endocarditis with doxycycline and hydrochloroquine.
  • 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
    • Prevention
      • Q fever vaccine is available in Australia for those with high occupational risk
  • Epidemiology
    • Incidence
      • found worldwide
    • Risk factors
      • exposure to farm animals
      • occupational exposure to animal products (e.g., animal hides)
      • immunosuppression
  • ETIOLOGY
    • 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
  • 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 the 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 a 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
  • Prognosis
    • May have prolonged course if untreated
    • Most cases resolve with treatment

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