Geography: mostly in south central and western states
Any case of pneumonic tularemia should be considered a possible bioterrorism event
Etiology
Francisella tularensis
As few as 10 oorganisms are capable of infection (by either cutaneous or aerosol route)
Physiology
Incubation Period: 3-5 days
Route of Infection:
Direct Contact with Tissues of Infected Small Animals: associated with skinning or eating (usually of rabbits or squirrels)
Bite of Infected Tick or Deerfly:
Inhalation of Contaminated Aerosols: landscapers or agricultural workers who generate aerosols in highly endemic areas are predisposed to pneumonic tularemia
Efficiency of aerosol transmission makes F. tularensis a potential biowarfare agent
Pneumonia: occurs due to inhalational exposure or bacteremia
Diagnosis
Sputum GS/Cult+Sens:
Fastidious, pleomorphic Gram-negative rod
Growth requires cysteine-enriched culture media at BSL-3 (preferably forwarded to a Level B lab, due to hazards to lab personnel)
Fluorescent Ab or Immunochemical Stains of Sputum or Tissue: may be positive
CXR/Chest CT Pattern: variable pattern, but usually normal at onset of the symptoms (typically 3-5 days after the exposure)
Diffuse Bronchopneumonia: often with hilar adenopathy
Pleural Involvement (Relatively Common): may occur without parenchymal involvement
Lobar Consolidation/Apical Infiltrates/Lung Abscess: less common patterns
Serology: acute and convalescent titers demonstrates 4-fold rise
Single titer of >1:160: compatible with past or current infection
Blood c/s: positive blood cultures are rare
Clinical Presentations
Ulceroglandular Tularemia: could potentially represent a bioterrorism event
Pneumonic Tularemia (very uncommon)
First Phase: abrupt onset of non-specific febrile illness (CXR usually normal during this phase)
Fever/Chills
Fatigue
Headache
Malaise
Second Phase: pneumonic symptoms (CXR abnormal during this phase)
Cough:
Chest Pain:
Dyspnea:
Treatment
Streptomycin (Aminoglycosides are the Preferred Agents): x 10 days
Gentamicin (x 10 days): acceptable alternative
Ciprofloxacin: acceptable alternative
Doxycycline or Chloramphenicol (x 14 days): acceptable alternatives (however, these agents require longer courses of therapy and have higher relapse rates)
Ceftriaxone: inadequate (despite its demonstrated in vitro activity)
Live-Attenuated Vaccine (Derived from Avirulent Strain): available for laboratory workers
Immunity develops over 2 wks
Provides incomplete protection against inhalational exposure (must also use antibiotic post-exposure prophylaxis)
Post-Exposure Prophylaxis: Doxycycline or Ciprofloxacin x 14 days
Patient should follow temperature for signs of fever
Vaccine is not effective alone for this purpose
Infection control: standard precautions (no human-to-human spread)
