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, 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

• Babesiosis
• Colorado tick fever
• Ehrlichiosis
• Heartland virus
• Lyme
• Murine typhus
• Rocky mountain spotted fever
• Southern tick-associated rash illness (STARI)
• Tick paralysis
• Tularemia

Bioterrorism Agents

Category A

• Anthrax
• Smallpox
• Plague
• Tularemia
• Botulinum Toxin
• Viral hemorrhagic fever

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

• Influenza
• Yellow fever
• Tickborne hemorrhagic fever
• Tickborne encephalitis

Diagnosis

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

Treatment

Antibiotics

Postexposure Prophylaxis

• Doxycycline 100mg PO q12hrs x 14 days OR
• Ciprofloxacin 500mg PO q12hrs q12hrs x 10 days

Active Disease

• Streptomycin 1g (15mg/kg) IM q12hrs daily x 10 days (First line) OR
• Gentamicin 5mg/kg/day IV/IM once daily x 10 days OR
• Ciprofloxacin 400mg (15mg/kg) q12hrs daily x 10 days OR
• Doxycycline 100mg (2.2mg/kg) IV q12hrs daily x 14 days OR
• Chloramphenicol 15mg/kg IV q6hrs daily x 14 days

Disposition

• Admit severe disease
• Can selectively treat mild disease

See Also

• Tick borne illnesses
• Bioterrorism

References

• http://www.cdc.gov/tularemia/index.html