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Francisella tularensis
infection in humans |
Francisella tularensis infections may be acquired by
the bite of infected ticks, but has also long been recognized
as a direct zoonotic infection of rabbit hunters and trappers.
- Hunters and trappers contract the disease while skinning
their kills.
Tularemia is also an occupational risk for veterinarians handling
infected animals, especially cats.
- In one study in Alaska, 14% of veterinarians had positive
antibody titers to F. tularensis, compared to 1% of the
general U.S. population.
- 7.7% of cases of tularemia in the U.S. between 1977 and 1998
were due to contact (bites/scratches) with infected cats, and
during an outbreak in Sweden in 2000, ownership of cats was a
specific risk factor for infection.
People may also be exposed by consuming undercooked game meats
(infection requires 10e8 organisms) or inhalation of the organism
(infection requires only 10e1-2 organisms)
Forms of disease in humans:
Fever/chills, headache and malaise are followed by more specific
symptoms related to the particular form of tularemia that develops:
Via direct skin contact with the organism or the bite of
an infected tick-
- ulceroglandular form (21-87% of cases)
- ulcerative skin lesions with lymphadenopathy and suppuration
Via oropharyngeal (ingestion or inhalation) or ocular contact
with the organism-
- oculoglandular form (<5% of cases) (via
conjunctival exposure)
- photophobia, lacrimation, conjunctivitis, scleral injection,
corneal ulceration and chemosis; preauricular or submandibular
lymphadenopathy
- exudative pharyngeal form (<12% of cases)
- severe sore throat and cervical, preparotid or retropharyngeal
lymphadenopathy
- systemic typhoidal form (5-30% of cases)
- multisystemic symptoms and organ involvement, often with
loose and watery, but non-bloody diarrhea, vomiting and abdominal
pain
- pneumonic form (7-20%, especially in farmers and laboratory
workers)
- fever, cough, hemoptysis, chest pain
A live-attenuated vaccine is available for high risk individuals,
but as with plague, it is not routinely recommended for veterinarians.
