Clinical Background
Francisella tularensis is a cause of potentially severe zoonotic disease in humans.
Epidemiology
- Incidence - <1/100,000 in United States
- Transmission - blood-sucking insects or contact with infected animals via inapparent abrasions
- Primarily a disease of wild animals
- Human vectors in U.S. are ticks and rabbits
Organism
- Gram-negative, non-sporeforming bacillus
- Two main biovars are F. tularensis-tularensis (type A) and F. tularensis-palearctica (type B)
Clinical Presentation
- Incubation is generally 2-10 days
- The disease often begins with the sudden onset of flu-like symptoms, chills, fever, headache and generalized aches
- Forms of tularemia
- Ulceroglandular (75-85%)
- Most common form of tularemia
- Direct contact or insect bite
- Small ulcer at portal of entry with associated lymphadenopathy
- Oculoglandular
- Conjunctival (entry via contaminated fingers) - 1%
- Unilateral intense conjunctivitis
- Oropharyngeal and gastrointestinal
- Follows ingestion of contaminated food
- Oral - exudative pharyngitis, cervical, preauricular adenopathy
- Gastrointestinal - ulcerative GI lesions, diarrhea
- Respiratory
- Inhalational exposure or extension from systemic disease
- Presents as infiltrates on chest X-ray
- Pneumonia with cough, pleuritic chest pain
- Typhoidal
- Rare in U.S.
- Usually associated with bacteremic gastrointestinal disease and consumption of poorly cooked wild game
- High fever, headache and shock
- Ulceroglandular (75-85%)
- Complications - septicemia, meningitis, endocarditis, hepatitis and renal failure
Treatment and Prevention
- Antibiotic treatment is necessary and curative for most cases
- Vaccination available for at-risk individuals
See Also
