Francisella tularensis

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Francisella tularensis

• First isolated from rodents in 1919 by Dr.
  Francis (Tulare County, CA)
• Considered the most virulent organism that
  infects humans
• 200 cases /year, in all 50 states

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Epidemiology
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Morphology and Physiology

• Gram-negative rod, pleomorphic (coccoid to
  filamentous)

• Facultative anaerobe
• Requires a rich medium plus cystine to grow

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Reservoirs and Transmission

• Wild mammals (rabbits, squirrels, muskrats,
  beavers, deer)
• Transmission by tick, deer fly, skin abrasion and
  transovarial

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..and of the hare

• ......of their flesh shall ye not eat, and
  their carcass shall ye not touch, they are
  unclean to you .
• (Leviticus XI6-8)

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Infection

• Infected insect bite
• Contact of abraded skin with infected material

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Major Clinical Manifestations

• Ulceroglandular (70-85)
• Glandular (5-10)
• Typhoidal (5-10)
• Pneumonic (1-5)
• Oculoglandular (1-2)
• Oropharyngeal (rare)

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Ulceroglandular tularemia

• Local ulceration
• Local lymphadenopathy
• Bacteremia and fever
• Disseminated lymphadenopathy

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Tularemic ulcer

• Primary lesion (papule) forms at point of entry
• Becomes an open ulcer in about a week

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Pneumonic tularemia

• Acquire either via the mechanisms of
  ulceroglandular or from direct respiratory route
  from skinning an infected rabbit or from another
  person with pneumonic tularemia
• High mortality

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Typhoidal tularemia

• Acquired by ingestion of food or water
  contaminated with high number of organisms due to
  animals that died from tularemia
• Symptoms similar to typhoid fever (GI distress
  and high fever)

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Treatment

• Difficult because organisms are intracellular
• Long term streptomycin therapy commonly used
• Immunity is cell-mediated, so killed vaccines of
  little value
• Attenuated strain vaccine available for high risk
  person

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Prevention

• Wear rubber gloves when in contact infected
  material
• Watch out for ticks