Tularemia

Background

  • Caused by the intracellular gram negative bacteria Francisella tularensis
  • Primarily spread through tick and deer fly bites
    • Ticks that spread Tularemia include:
  1. Dog tick (Dermacentor variabilis)
  2. Wood tick (Dermacentor andersoni)
  3. Lone star tick (Amblyomma americanum)
  • Also spread through contact with infected animals (rabbits, rodents), ingestion of contaminated water, inhalation of aerosolized material (ex. running over dead animal with lawn mower)

Potential Bioterrorism Threat

  • Listed by CDC as potential bioterrorism threat as the bacterium can be aerosolized, is highly infective, and highly incapacitating.

Clinical Features

  • Features depend on site of infection
  • All are associated with fevers

Ulceroglandular

  • Most common form, represents about 75% of disease
  • Present with a single erythematous ulcerative lesion with a central eschar
    • This represents direct inoculation from the insect bite or from handling infected animals
  • Lymphadenopathy
    • Usually inguinal or axillary
    • Cervical or occipital in children

Glandular

  • Regional lymphadenopathy with no skin lesions or ulceration
  • Most common presentation among children
  • Suppurated nodes may need drainage

Oropharyngeal

  • From ingesting contaminated material
    • May cause outbreaks when water supply is disrupted
  • Symptoms include:
    • Sore throat,
    • Mouth ulcers
    • Exudative pharyngitis/tonsilitis
    • Cervical lymphadenitis

Pneumonic

  • Associated with highest mortality rate
  • Results from direct inhalation of the bacterium into the lungs
    • Farmers and herders at higher risk
  • Acute infection associated with non-specific flu-like symptoms
  • Progresses to more severe pneumonic signs
    • Nodular infiltrates with pleural effusion on chest xray
      • Exudative effusion with lymphocytic predominance
  • May also be secondary to hematologic dissemination from other source

Oculoglandular

  • Occurs with inocculation into eye (aerosols, rubbing with contaminated fingers, splash, etc.)
  • Pain, photophobia, tearing
  • May have small ulcers of the conjunctiva or periorbital erythema
    • May lead to corneal ulceration
  • May have preauricular, cervical or submandibular lymphadenopathy

Thyphoidal

  • Tularemia that does not fit into any of the other groups
    • May present as sepsis

Differential Diagnosis

Tick Borne Illnesses

Bioterrorism Agents[1]

Category A

Category B

  • Ricin
  • Brucellosis
  • Epsilon toxin
  • Psittacosis
  • Q Fever
  • Staph enterotoxin B
  • Typhus
  • Glanders
  • Melioidosis
  • Food safety threats
  • Water safety threats
  • Viral encephalitis

Category C

Evaluation

  • Titers
  • PCR
  • Gram stain does not usually reveal any organisms

Management

Antibiotics

Postexposure Prophylaxis

Active Disease

Disposition

  • Admit severe disease
  • Can selectively treat mild disease

See Also

External Links

References