Tularemia
Background
- Caused by the intracellular gram negative bacteria Francisella tularensis
- Primarily spread through tick and deer fly bites
- Ticks that spread Tularemia include:
- Dog tick (Dermacentor variabilis)
- Wood tick (Dermacentor andersoni)
- Lone star tick (Amblyomma americanum)
- Ticks that spread Tularemia include:
- 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
- At risk patient groups include farmers, meat handlers, landscapers, veterinarians, hunters, sheep shearers and taxidermists.
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
- Nodular infiltrates with pleural effusion on chest xray
- 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
Typhoidal
- Tularemia that does not fit into any of the other groups
- May present as sepsis
- Often has associated GI symptoms
- No skin lesions
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[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
- Influenza
- Yellow fever
- Tickborne hemorrhagic fever
- Tickborne encephalitis
Evaluation
- Titers
- PCR
- Gram stain does not usually reveal any organisms
Management
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